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AP® Calculus AB-BC

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Difficult

Trig Derivatives Taken Up Another Notch

APCALC-DJXQBB

Which of the following are equivalent to $\cfrac{d}{dx} (\sin x)$?

I. $y'$ when $y=\sin x +\cos \pi$
II. $\cfrac{dy}{dx}$ when $y-\cos x \cdot \tan x = 15$
III. $f'(x)$ when $f(x)=\sin x(\cos^2 (3x) + \sin^2 (3x))$

A

I only.

B

I and II only.

C

I and III only.

D

I, II, and III.