13 Limits and Derivatives
Miscellaneous Exercise
Question:
Find derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (x^2+1)cos x
Answer:
- Use the chain rule to calculate the derivative:
d/dx[(x^2 + 1)cos x] = d/dx[(x^2 + 1)]cos x + (x^2 + 1)d/dx[cos x]
- Calculate the derivative of the first term:
d/dx[(x^2 + 1)] = 2x
- Calculate the derivative of the second term:
d/dx[cos x] = -sin x
- Substitute the derivatives into the equation:
d/dx[(x^2 + 1)cos x] = 2xcos x - (x^2 + 1)sin x
Question:
Find the derivative of the following functions from first principle: cos(x−π/8)
Answer:
Step 1: Identify the function, f(x) = cos(x−π/8).
Step 2: Use the definition of the derivative to calculate the derivative of f(x):
df/dx = lim h→0 (cos(x-π/8 + h) - cos(x-π/8))/h
Step 3: Use the sum and difference identities for cosine to simplify the equation:
df/dx = lim h→0 (cos(x+h-π/8) - cos(x-π/8))/h
Step 4: Use the product to sum identity for cosine to further simplify the equation:
df/dx = lim h→0 (cos(x-π/8)cos(h) - cos(x-π/8)cos(h))/h
Step 5: Simplify the equation:
df/dx = lim h→0 (cos(x-π/8)(1 - cos(h))/h
Step 6: Use the power reduction identity for cosine to simplify the equation:
df/dx = lim h→0 (cos(x-π/8)(2sin2(h/2))/h
Step 7: Use the double angle identity for sin to simplify the equation:
df/dx = lim h→0 (cos(x-π/8)(2sin(h)cos(h))/h
Step 8: Use the limit definition of the derivative to calculate the derivative of f(x):
df/dx = lim h→0 (2sin(h)cos(x-π/8))/h = 2cos(x-π/8)lim h→0 (sin(h))/h = 2cos(x-π/8)·1 = 2cos(x-π/8)
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers : (x+a)
Answer:
Answer:
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First, use the power rule: Derivative of (x+a) = d/dx (x+a) = 1
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Since a is a constant, the derivative is equal to 1. Therefore, the derivative of (x+a) = 1
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,r and s are fixed non-zero constants and m and n are integers) : a/x^4−b/x^2+cos x
Answer:
Answer: Derivative of a/x^4 = -4a/x^5 Derivative of b/x^2 = -2b/x^3 Derivative of cos x = -sin x
Therefore, the derivative of the given function is -4a/x^5 -2b/x^3 -sin x.
Question:
Find the derivative of the following functions(it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : cosx/(1+sin x)
Answer:
Step 1: Rewrite the given function as cos x/1+sin x
Step 2: Use the quotient rule to find the derivative of the function
Derivative = (1+sin x)(-cos x) - (cos x)(-sin x) / (1+sin x)^2
Step 3: Simplify the derivative
Derivative = -cos^2 x - sin^2 x / (1+sin x)^2
Step 4: Use the double angle identity to simplify the derivative
Derivative = -1 / (1+sin x)^2
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : cosec x cot x
Answer:
Step 1: Use the product rule to find the derivative of cosec x cot x.
Step 2: Differentiate cosec x with respect to x.
Step 3: Differentiate cot x with respect to x.
Step 4: Multiply the derivatives of cosec x and cot x.
Step 5: Simplify the expression.
Answer: The derivative of cosec x cot x is -cosec x cosec x.
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : sin^n x
Answer:
-
Use the chain rule: d/dx (sin^n x) = n sin^(n-1) x cos x
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Simplify: n sin^(n-1) x cos x
Question:
Find the derivative of the following functions(it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (ax+b)/(cx+d)
Answer:
Step 1: Rewrite the function in the form of a fraction (ax+b)/(cx+d)
Step 2: Apply the quotient rule
Derivative = [(c(ax+b)) - (d(cx+d))]/[(cx+d)^2]
Step 3: Simplify the expression
Derivative = [(acx+bc) - (dcx+bd)]/[(cx+d)^2]
Step 4: Simplify further
Derivative = (ad-bc)/[(cx+d)^2]
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (sec x−1)/(sec x+1)
Answer:
Answer:
- First, use the quotient rule to find the derivative of (sec x - 1)/(sec x + 1):
d/dx [(sec x - 1)/(sec x + 1)] = (sec x + 1)(d/dx sec x) - (sec x - 1)(d/dx sec x) / (sec x + 1)^2
- Now, use the chain rule to find the derivative of sec x:
d/dx sec x = sec x tan x (d/dx x)
- Substitute this into the equation from step 1:
d/dx [(sec x - 1)/(sec x + 1)] = (sec x + 1)(sec x tan x)(d/dx x) - (sec x - 1)(sec x tan x)(d/dx x) / (sec x + 1)^2
- Simplify the equation:
d/dx [(sec x - 1)/(sec x + 1)] = (sec x tan x)(d/dx x) / (sec x + 1)^2
- Finally, use the power rule to simplify the equation further:
d/dx [(sec x - 1)/(sec x + 1)] = (sec^2 x tan x)(d/dx x) / (sec^2 x + 1)
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (ax+b)(cx+d)^2
Answer:
Answer:
Step 1: Rewrite the function as: (ax+b)(cx^2 + 2dx + d^2)
Step 2: Apply the product rule: d/dx [(ax+b)(cx^2 + 2dx + d^2)] = (ax+b) * (2cx + 2d) + (cx^2 + 2dx + d^2) * (a)
Step 3: Simplify the expression: d/dx [(ax+b)(cx^2 + 2dx + d^2)] = 2acx^2 + (2ad + 2bc)x + (2bd + ab)
Question:
Find the derivative of the following function from first principle: −x
Answer:
Step 1: Identify the function
Function: f(x) = -x
Step 2: Compute the difference quotient
Difference Quotient: (f(x + h) - f(x))/h
Step 3: Simplify the difference quotient
Difference Quotient: (-(x + h) - (-x))/h
Step 4: Take the limit of the difference quotient as h approaches 0
Limit of Difference Quotient: lim h→0 (-(x + h) - (-x))/h
Step 5: Simplify the limit
Limit of Difference Quotient: lim h→0 (-h)/h
Step 6: Compute the limit
Limit of Difference Quotient: lim h→0 -1
Step 7: The derivative of the function is
Derivative of f(x) = -x: -1
Question:
Find the derivative of the following functions form first principle: (−x)^(−1)
Answer:
Answer: Step 1: Let f(x) = (−x)^(−1)
Step 2: Find f’(x) using the first principle: f’(x) = lim h->0 [f(x+h) - f(x)]/h
Step 3: Substitute the function f(x) in the equation: f’(x) = lim h->0 [((−x+h)^(−1)) - (−x)^(−1)]/h
Step 4: Simplify the equation: f’(x) = lim h->0 [((−1/x+h)^(−1)) - (−1/x)^(−1)]/h
Step 5: Simplify further: f’(x) = lim h->0 [1/(−1/x+h) - 1/(−1/x)]/h
Step 6: Solve for f’(x): f’(x) = lim h->0 [(-x - hx)/(x + hx)(-x)]/h
Step 7: Simplify: f’(x) = lim h->0 [(-1)/(x + hx)]/h
Step 8: Solve for f’(x): f’(x) = lim h->0 [-1/(x + hx)]/h
Step 9: Simplify further: f’(x) = -1/x^2
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (a+b sin x)/(c+d cos x)
Answer:
-
Rewrite the function as: (a+b sin x)(c-d cos x) / (c+d cos x)(c+d cos x)
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Take the derivative of each term in the numerator and denominator: Numerator: (a+b sin x)’ (c-d cos x) + (c-d cos x)’ (a+b sin x) Denominator: (c+d cos x)’ (c+d cos x)
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Simplify the derivatives: Numerator: b cos x (c-d cos x) - d sin x (a+b sin x) Denominator: 2d cos x (c+d cos x)
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Simplify the fraction: (b cos x (c-d cos x) - d sin x (a+b sin x)) / (2d cos x (c+d cos x))
Question:
Find the derivative of the following functions(it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (px^2+qx+r)/(ax+b)
Answer:
Step 1: Rewrite the function as: (px^2 + qx + r)(ax + b)^-1
Step 2: Take the derivative of both sides: 2px(ax + b)^-1 + q(ax + b)^-1 - (px^2 + qx + r)(ax + b)^-2(-a)
Step 3: Simplify the expression: 2px(ax + b)^-1 + q(ax + b)^-1 + (px^2 + qx + r)(-a)(ax + b)^-2
Step 4: Simplify further: 2px(ax + b)^-1 + q(ax + b)^-1 - (pa^2x^2 + qax + ra)(ax + b)^-2
Question:
Find the derivative of the following fucctions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (1+1/x)/(1−1/x)
Answer:
Given, f(x) = (1+1/x)/(1−1/x)
Step 1: Rewrite the function as
f(x) = (1+1/x) (1/1−1/x)
Step 2: Take the derivative of both sides
f’(x) = (1/x) (1/1−1/x) + (1+1/x) (-1/x2) (1/1−1/x)
Step 3: Simplify the equation
f’(x) = (1/x2)(1+1/x−1−1/x)
Step 4: Simplify further
f’(x) = (1/x2)(2−1/x)
Step 5: Final answer
f’(x) = (2−1/x)/x2
Question:
Find the derivative of the following functions from first principle: sin(x+1)
Answer:
-
Rewrite the function as f(x) = sin(x+1)
-
Take the derivative of f(x) using the definition of the derivative: f’(x) = lim h->0 (sin(x+1+h) - sin(x+1))/h
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Simplify the expression: f’(x) = lim h->0 (sin(x+h+1) - sin(x+1))/h
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Use the identity sin(a+b) = sin(a)cos(b) + cos(a)sin(b): f’(x) = lim h->0 (sin(x+1)cos(h) + cos(x+1)sin(h) - sin(x+1))/h
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Simplify the expression: f’(x) = lim h->0 (cos(x+1)sin(h))/h
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Use the identity sin(a) = a when a is small: f’(x) = lim h->0 (cos(x+1)h)/h
-
Simplify the expression: f’(x) = lim h->0 cos(x+1)
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Evaluate the limit: f’(x) = cos(x+1)
Question:
Find the derivative of the following function (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (ax+b)/(cx+d)
Answer:
Given: f(x) = (ax+b)/(cx+d)
Step 1: Rewrite the function in the form of f(x) = u/v
f(x) = (ax+b)/(cx+d) = (ax+b)/v, where v = (cx+d)
Step 2: Apply the quotient rule to calculate the derivative of the function.
f’(x) = [v(du/dx) - u(dv/dx)]/v^2
Step 3: Substitute the values of u and v in the equation.
f’(x) = [v(a) - (ax+b)(c)]/v^2
Step 4: Simplify the equation.
f’(x) = [cx+d)(a) - (ax+b)(c)]/[(cx+d)^2]
f’(x) = [acx+ad - acx - bc]/[(cx+d)^2]
f’(x) = ad/[(cx+d)^2]
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (ax^2+sin x)(p+q cos x)
Answer:
Step 1: Use the Product Rule to differentiate the given expression.
Step 2: Differentiate the first factor, (ax^2 + sin x), using the Power Rule.
Step 3: Differentiate the second factor, (p + q cos x), using the Chain Rule.
Step 4: Combine the two derivatives to obtain the final answer.
Answer: (2ax + cos x)(p + q cos x) + (ax^2 + sin x)(-q sin x)
Question:
If the derivative of the function 4√x−2 is a/√x. Find the value of a.
Answer:
- Use the definition of a derivative to find a:
a = (4√x - 2)’ = 4/2√x
- Substitute x = 1 in the equation to solve for a:
a = 4/2√1
- Simplify to find the value of a:
a = 4
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) :(4x+5 sin x)/(3x+7 cosx)
Answer:
- Rewrite the function in its simplest form:
(4x + 5sin x) / (3x + 7cos x)
- Use the Quotient Rule to find the derivative:
[(3x + 7cos x)(4) - (4x + 5sin x)(-7cos x)] / (3x + 7cos x)^2
- Simplify the derivative:
[12x + 28cos x + 28x - 35sin x] / (3x + 7cos x)^2
- Simplify further:
[40x + 28cos x - 35sin x] / (3x + 7cos x)^2
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) :x/(1+tan x)
Answer:
Step 1: Rewrite the function as x/1+tan x
Step 2: Apply the quotient rule to the function
Step 3: Find the derivative of the numerator
Derivative of numerator = 1
Step 4: Find the derivative of the denominator
Derivative of denominator = sec^2 x
Step 5: Substitute the derivatives of the numerator and denominator into the quotient rule
Derivative of x/(1+tan x) = 1/sec^2 x - x sec^2 x/(1+tan x)^2
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r,s and s are fixed non-zero constants and m and n are integers) : x^4(5 sin x−3 cos x)
Answer:
Answer: Step 1: Take the derivative of x^4 Derivative of x^4 = 4x^3
Step 2: Take the derivative of 5 sin x Derivative of 5 sin x = 5 cos x
Step 3: Take the derivative of -3 cos x Derivative of -3 cos x = -3 (-sin x)
Step 4: Combine the derivatives Derivative of x^4 (5 sin x - 3 cos x) = 4x^3 (5 cos x - 3 (-sin x))
Step 5: Simplify Derivative of x^4 (5 sin x - 3 cos x) = 20x^3 sin x + 9x^3 cos x
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : sin(x+a)/cosx
Answer:
Step 1: Rewrite the given expression as sin(x+a) * cosx^-1.
Step 2: Apply the quotient rule for derivatives.
Step 3: Derivative of sin(x+a) = cos(x+a)
Step 4: Derivative of cosx^-1 = -cosx^-2
Step 5: Multiply the derivatives of the numerator and denominator.
Step 6: Simplify the expression.
Answer: The derivative of sin(x+a)/cosx is cos(x+a) * -cosx^-2 = -sin(x+a)cosx^-2.
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (x+cosx)(x−tanx)
Answer:
- Use the product rule to find the derivative of (x + cosx)(x − tanx):
d/dx [(x + cosx)(x − tanx)] = (x + cosx)d/dx (x − tanx) + (x − tanx)d/dx (x + cosx)
- Find the derivative of the first term:
(x + cosx)d/dx (x − tanx) = (x + cosx)(1 − sec2x)
- Find the derivative of the second term:
(x − tanx)d/dx (x + cosx) = (x − tanx)(1 + cosx)
- Add the two derivatives together:
d/dx [(x + cosx)(x − tanx)] = (x + cosx)(1 − sec2x) + (x − tanx)(1 + cosx)
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constant and m and n are integers) : (ax+b)^n
Answer:
Answer:
Step 1: Use the power rule to find the derivative.
Derivative = n(ax + b)^(n-1) * a
Step 2: Simplify the derivative.
Derivative = an(ax + b)^(n-1)
Question:
Find the derivative of the following function (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (x^2cos(π/4))/sin x
Answer:
Given, f(x) = (x^2cos(π/4))/sin x
Step 1: Rewrite the function using the product rule
f(x) = (x^2cos(π/4))/sin x = x^2cos(π/4) . (1/sin x)
Step 2: Apply the product rule
f’(x) = [2xcos(π/4) . (1/sin x)] + [x^2cos(π/4) . (-cos x/sin^2 x)]
Step 3: Simplify the expression
f’(x) = [2xcos(π/4) . (1/sin x)] + [x^2cos(π/4) . (-cos x/sin^2 x)] = (2xcos(π/4))/sin x - (x^2cos(π/4)cos x)/sin^3 x
Hence, the derivative of the given function is f’(x) = (2xcos(π/4))/sin x - (x^2cos(π/4)cos x)/sin^3 x
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (px+q)(r/x+s)
Answer:
Step 1: Rewrite the function in terms of multiplication and division:
px + q × (r/x + s)
Step 2: Use the product rule to differentiate the function:
(px + q)’ × (r/x + s) + (px + q) × (r/x + s)'
Step 3: Differentiate each term:
p + q’ × (r/x + s) + (px + q) × (r/x-2s)
Step 4: Simplify:
p + q’ × (r/x + s) + (px + q) × (r/x-2s)
= p + qr/x2 - 2qs + pxr/x2 - 2qsr/x2
Step 5: Simplify further:
p + qr/x2 - 2qs + pxr/x2 - 2qsr/x2
= p + qr/x2 + pxr/x2 - 2qs - 2qsr/x2
= p(1 + xr/x2) + q(r/x2 - 2sr/x2)
= p + qr/x2 - 2qs/x2
Question:
Find the derivative of the following functions(it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers): 1/(ax^2+bx+c)
Answer:
-
Rewrite the function in the form of y = (d/dx)(ax^2+bx+c)
-
Differentiate both sides of the equation with respect to x
y’ = (d/dx)(2ax + b)
- Substitute the values of a, b and c
y’ = (d/dx)(2a*x + b)
- Simplify the expression
y’ = 2a
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : sin(x+a)
Answer:
-
Use the Chain Rule: d/dx[sin(x+a)] = d/du[sin(u)] * du/dx[x+a]
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Differentiate the inside function: d/du[sin(u)] = cos(u)
-
Differentiate the outside function: du/dx[x+a] = 1
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Substitute: d/dx[sin(x+a)] = cos(x+a)
Question:
Find the derivative of the following (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (sin x+cos x)/(sinx−cosx)
Answer:
Answer: Step 1: Rewrite the expression as: (sin x+cos x)/(sinx−cosx) = (a sin x + b cos x)/(c sin x − d cos x) Step 2: Use the Quotient Rule to find the derivative: d/dx [(a sin x + b cos x)/(c sin x − d cos x)] = (p sin x + q cos x)(c sin x − d cos x) - (a sin x + b cos x)(r sin x + s cos x)/[(c sin x − d cos x)^2] Step 3: Simplify the expression: d/dx [(a sin x + b cos x)/(c sin x − d cos x)] = (p sin x + q cos x)(c sin x − d cos x) - (a sin x + b cos x)(r sin x + s cos x)/[(c sin x − d cos x)^2] = (p c - q d) sin x cos x + (q c - p d) sin^2 x - (a r + b s) sin x cos x - (b r + a s) cos^2 x/[(c sin x − d cos x)^2]
Question:
Find the derivative of the following fuctions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : x/sin^2x
Answer:
Step 1: Rewrite the function as x/sin^2x = x(sin^2x)^-1
Step 2: Take the derivative of both sides of the equation using the chain rule: d/dx[x(sin^2x)^-1] = (sin^2x)^-1d/dx[x] + xd/dx[(sin^2x)^-1]
Step 3: Simplify the equation on the right hand side: d/dx[x(sin^2x)^-1] = (sin^2x)^-11 + x(-2sinxcosx)*(sin^2x)^-2
Step 4: Simplify the equation further: d/dx[x(sin^2x)^-1] = (sin^2x)^-1 - 2xsinxcosx*(sin^2x)^-2
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are fixed integers) : (x+secx)(x−tanx)
Answer:
Step 1: Rewrite the function as: (x + secx)*(x - tanx)
Step 2: Use the Product Rule to find the derivative of the function: d/dx [(x + secx)(x - tanx)] = (d/dx [x + secx])(x - tanx) + (x + secx)*(d/dx [x - tanx])
Step 3: Use the Chain Rule to find the derivatives of the individual terms: d/dx [x + secx] = 1 + (d/dx [secx]) d/dx [x - tanx] = 1 - (d/dx [tanx])
Step 4: Use the Chain Rule to find the derivatives of secx and tanx: d/dx [secx] = secx*tanx d/dx [tanx] = sec^2x
Step 5: Substitute the derivatives of secx and tanx into the equation: d/dx [(x + secx)(x - tanx)] = (1 + secxtanx)(x - tanx) + (x + secx)(1 - sec^2x)
Step 6: Simplify the equation: d/dx [(x + secx)(x - tanx)] = x - tanx + secxtanx + x - secx*sec^2x
Step 7: Simplify the equation further: d/dx [(x + secx)(x - tanx)] = 2x - (tanx + secxsec^2x)
Question:
Find the derivative of the following functions (it is to be understood that a,b,c,d,p,q,r and s are fixed non-zero constants and m and n are integers) : (ax+b)^n(cx+d)^m
Answer:
Answer:
-
Use the power rule to expand the function: Derivative of (ax + b)^n = n(ax + b)^(n-1) * (a) Derivative of (cx + d)^m = m(cx + d)^(m-1) * (c)
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Multiply the two derivatives: n(ax + b)^(n-1) * (a) * m(cx + d)^(m-1) * (c)
-
Simplify the expression: nm(ax + b)^(n-1) * (cx + d)^(m-1) * (ac)
JEE NCERT Solutions (Mathematics)
01 Sets
02 Relations and Functions
03 Trigonometric Functions
04 Principle of Mathematical Induction
05 Complex Numbers and Quadratic Equations
06 Linear Inequalities
07 Permutations and Combinations
08 Binomial Theorem
09 Sequences and Series
10 Straight Lines Exercise
10 Straight Lines Miscellaneous
11 Conic Sections
12 Introduction to Three Dimensional Geometry
13 Limits and Derivatives
14 Mathematical Reasoning
15 Statistics
16 Probability