AM-2695

R-formula

A Math · Secondary 4 · Hard · R-formula

Given that

y = 8\cos\theta + 15\sin\theta

, express

y

in the form

R\cos(\theta - \alpha)

, where

R>0

and

0^\circ<\alpha<90^\circ

.

$17\cos\bigl(\theta-\tan^{-1}(15/8)\bigr)$
$17\sin\bigl(\theta-\tan^{-1}(15/8)\bigr)$
$17\cos\bigl(\theta+\tan^{-1}(15/8)\bigr)$
$17\sin\bigl(\theta+\tan^{-1}(15/8)\bigr)$

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