Question

If $$y = \sin \,2x$$   then $$\frac{{{d^6}y}}{{d{x^6}}}$$  at $$x = \frac{\pi }{2}$$  is equal to :

A. $$-64$$
B. $$0$$  
C. $$64$$
D. none of these
Answer :   $$0$$
Solution :
$$\eqalign{ & \frac{{dy}}{{dx}} = 2\cos \,2x = 2\sin \left( {2x + \frac{\pi }{2}} \right) \cr & \therefore \frac{{{d^2}y}}{{d{x^2}}} = {2^2}\cos \left( {2x + \frac{\pi }{2}} \right)\,\,\, = {2^2}\sin \left( {2x + 2.\frac{\pi }{2}} \right) \cr & \frac{{{d^6}y}}{{d{x^6}}} = {2^6}.\sin \left( {2x + 6.\frac{\pi }{2}} \right) = {2^6}\sin \left( {2x + 3\pi } \right) \cr} $$

Releted MCQ Question on
Calculus >> Differentiability and Differentiation

Releted Question 1

There exist a function $$f\left( x \right),$$  satisfying $$f\left( 0 \right) = 1,\,f'\left( 0 \right) = - 1,\,f\left( x \right) > 0$$       for all $$x,$$ and-

A. $$f''\left( x \right) > 0$$   for all $$x$$
B. $$ - 1 < f''\left( x \right) < 0$$    for all $$x$$
C. $$ - 2 \leqslant f''\left( x \right) \leqslant - 1$$    for all $$x$$
D. $$f''\left( x \right) < - 2$$   for all $$x$$
Releted Question 2

If $$f\left( a \right) = 2,\,f'\left( a \right) = 1,\,g\left( a \right) = - 1,\,g'\left( a \right) = 2,$$         then the value of $$\mathop {\lim }\limits_{x \to a} \frac{{g\left( x \right)f\left( a \right) - g\left( a \right)f\left( x \right)}}{{x - a}}$$      is-

A. $$-5$$
B. $$\frac{1}{5}$$
C. $$5$$
D. none of these
Releted Question 3

Let $$f:R \to R$$   be a differentiable function and $$f\left( 1 \right) = 4.$$   Then the value of $$\mathop {\lim }\limits_{x \to 1} \int\limits_4^{f\left( x \right)} {\frac{{2t}}{{x - 1}}} dt$$     is-

A. $$8f'\left( 1 \right)$$
B. $$4f'\left( 1 \right)$$
C. $$2f'\left( 1 \right)$$
D. $$f'\left( 1 \right)$$
Releted Question 4

Let [.] denote the greatest integer function and $$f\left( x \right) = \left[ {{{\tan }^2}x} \right],$$    then:

A. $$\mathop {\lim }\limits_{x \to 0} f\left( x \right)$$     does not exist
B. $$f\left( x \right)$$  is continuous at $$x = 0$$
C. $$f\left( x \right)$$  is not differentiable at $$x =0$$
D. $$f'\left( 0 \right) = 1$$

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Differentiability and Differentiation


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