Question

Find derivative of cos x

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Answer 1

Answer:

Derivative Of cos x is :

-sin x

Answer 2

Answer:

-sinx

Step-by-step explanation:

it's Direct if u want first principle method here it follows

f'(x)=(cos(x+h)-cosx)/h

now use Cos C - cos D = 2 sin(c+d/2)sin(d-c/2)

f'(x) = [2 sin ( (2x+h)/2) sin (-h/2)]/h

f'(x) =[ -2 sin ((2x+h)/2) sin(h/2)]/h

f'(x) = -sin((2x+h)/2) [sin(h/2)/(h/2)].....now lim sinx/x when x--> 0 is 1

f'(x) = -sin((2x+h)/2)

h is negligible

f'(x) = -sinx

hope it helps u

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