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

(1) If x = et sin t, y = etcos t, t is a parameter, then dy/dx at (1, 1) is equal to
[A] –1/2
[B] –1/4
[C] 0
[D] 1/2
Answer: 0
(2) If y = e3x+n, then the value of dy/dx|x=0 is
[A] 1
[B] 0
[C] -1
[D] 3e7
Answer: 0

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(3) If x = is equal to dx
[A] –y/x
[B] y/x
[C] –x/y
[D] x/y
Answer: –x/y
(4) The derivative of y = (1 – x) (2 – x)…. (n – x) at x = 1 is equal to
[A] 0
[B] (-1) (n – 1)!
[C] n ! – 1
[D] (-1)n-1 (n – 1)!
Answer: (-1) (n – 1)!
(5) xy. yx = 16, then the value of dy/dx at (2, 2) is
[A] -1
[B] 0
[C] -1
[D] None of these
Answer: -1
(6) If y = then dy/dx is equal to
[A] 1/2 sec² x
[B] sec² x
[C] sec x tan x
[D] e1/2 log(1+tan²x)
Answer: sec x tan x
(7) If x sin (a + y) = sin y, then dy/dx is equal to
[A] sin2(a+y)/sina
[B] sina/sin2(a+y)
[C] sin(a+y)/sina
[D] sina/sin(a+y)
Answer: sin2(a+y)/sina
(8) The derivative of cos-1 (2x² – 1) w.r.t cos-1 x is
[A] 2
[B]
[C] 2x
[D] 1 – x²
Answer: 2
(9) If f(x) = x² sin1/x, where x ≠ 0, then the value of the function f(x) at x = 0, so that the function is continuous at x = 0 is
[A] 0
[B] -1
[C] 1
[D] None of these
Answer: 0
(10) The function f(x) = is
[A] discontinuous at only one point at x = 0
[B] discontinuous at exactly two points
[C] discontinuous at exactly three points
[D] None of these
Answer: discontinuous at only one point at x = 0
(11) The value of c in Rolle’s theorem for the function f(x) = x³ – 3x in the interval [o, √3] is
[A] 1
[B] -1
[C] 3/2
[D] 1/3
Answer: 1
(12) If ax² + 2hxy + by² = 1, then dy/dx equals
[A] hx+by/ax+by
[B] ax+by/hx+by
[C] ax+hy/hx+hy
[D] −(ax+hy)/hx+by
Answer: −(ax+hy)/hx+by
(13) If y = sin-1 then dy/dx is equal to
[A] 1
[B] 0
[C] π/2
[D] None of these
Answer: 0
(14) If y = aex+ be-x + c Where a, b, c are parameters, they y’ is equal to
[A] aex – be-x
[B] aex + be-x
[C] -(aex + be-x)
[D] aex – bex
Answer: aex – be-x
(15) If x = a cos4 θ, y = a sin4 θ. then dy/dx at θ = 3π/4 is
[A] -1
[B] 1
[C] -a²
[D] a²
Answer: -1
(16) Let y = t10 + 1 and x = t8 + 1, then  d2y/dx2 , is equal to
[A] d2y/dx2
[B] 20t8
[C] 5/16t6
[D] None of these
Answer: None of these
(17) If x = sin-1 (3t – 4t³) and y = cos-1 then dy/dx is equal to
[A] 1/2
[B] 2/5
[C] 3/2
[D] 1/3
Answer: 1/3
(18) If y = log then dy/dx is equal to
[A] 7
[B] 3/x−2
[C] 3/(x−1)
[D] None of these
Answer: None of these
(19) The derivative of sin-1 with respect to cos-1 is
[A] -1
[B] 1
[C] 2
[D] 4
Answer: 1
(20) If xy = ex-y then dy/dx is
[A] 1+x/1+logx
[B] 1−logx/1+logy
[C] not defined
[D] −y/(1+logx)2
Answer: −y/(1+logx)2

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