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NCERT Solutions for class 12 Maths | Chapter 5 - Continuity and Differentiability

(1) If y = (1 + x) (1 + x²) (1 + x4) …….. (1 + x2n), then the value of dy/dx at x = 0 is
[A] 0
[B] -1
[C] 1
[D] None of these
Answer: 1
(2) If y = e3x+n, then the value of dy/dx|x=0 is
[A] 1
[B] 0
[C] -1
[D] 3e7
Answer: (A + B)-1 = B-1 + A-1

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(3) If y = (tan x)sin x, then dy/dx is equal to
[A] sec x + cos x
[B] sec x+ log tan x
[C] (tan x)sin x
[D] None of these
Answer: None of these
(4) If f(x) = cos x, cos 2 x, cos 4 x, cos 8 x, cos 16 x, then the value of'(π/4) is
[A] 1
[B] √2
[C] 1/√2
[D] 0
Answer: √2
(5) The derivative of ex3 with respect to log x is
[A] ee3
[B] 3x22ex3
[C] 3x3ex3
[D] 3x2ex3+ 3x2
Answer: 3x3ex3
(6) If f(x) = tan-1 0 ≤ x ≤ π/2, then f'(π/6) is
[A] –1/4
[B] –1/2
[C] 1/4
[D] 1/2
Answer: 1/2
(7) If y = tan-1 then y'(1) is equal to
[A] 0
[B]
[C] -1
[D] -1/4
Answer: -1/4
(8) If xmyn = (x + y)m+n, then dy/dx is equal to
[A] x+y/xy
[B] xy
[C] x/y
[D] y/x
Answer: y/x
(9) If sec (x−y/x+y) = a then dy/dx is
[A] –y/x
[B] x/y
[C] –x/y
[D] y/x
Answer: y/x
(10) Let f(x)= and g (x) = ex. Then the value of (g o f)’ (0) is
[A] 1
[B] -1
[C] 0
[D] None of these
Answer: 0
(11) If f(x) = + cos² (2x + 1), then f'(0) =
[A] 5 + 2 sin 2
[B] 5 + 2 cos 2
[C] 5 – 2 sin 2
[D] 5 – 2 cos 2
Answer: 5 – 2 sin 2
(12) If y = ax² + b, then dy/dx at x = 2 is equal to ax
[A] 4a
[B] 3a
[C] 2a
[D] None of these
Answer: 4a
(13) If f(x) = then the value of f’ (√π/2) is
[A] √π/6
[B] –√π/6
[C] 1/√6
[D] π/√6
Answer: –√π/6
(14) If f(x) = then is equal to
[A] 1/24
[B] 1/5
[C] –√24
[D] 1/√24
Answer: 1/√24
(15) Differential coefficient of is
[A] 1/4√x = sec √x sin √x
[B] 1/4√x = (sec√x)3/2 sin√x
[C] 1/2√x sec√x sin √x.
[D] 1/2√x (sec√x)3/2 sin√x
Answer: 14√x = (sec√x)3/2 sin√x
(16) If f(x) = x ≠ 0 be continuous at x = 0, then f(o) =
[A] 1/2
[B] 1/4
[C] 2
[D] 3/2
Answer: 1/4
(17) If y = tan-1 then dy/dx is equal to
[A] 1/2
[B] π/4
[C] 0
[D] 1
Answer: 1
(18) If x = exp then dy/dx equals
[A] 2x [1 + tan (log x)] + x sec² (log x)
[B] x [1 + tan (log x)] + sec² (log x)
[C] 2x [1 + tan (logx)] + x² sec² (log x)
[D] 2x [1 + tan (log x)] + sec² (log x)
Answer: 2x [1 + tan (log x)] + x sec² (log x)
(19) If sin y + e-xcos y = e, then dy/dx at (1, π) is equal to
[A] sin y
[B] -x cos y
[C] e
[D] sin y – x cos y
Answer: e
(20) If y = 2x32x-1 then dy/dx is equal to dx
[A] (log 2) (log 3)
[B] (log lg)
[C] (log 18²) y²
[D] y (log 18)
Answer: y (log 18)

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