AM-2659

R-formula

A Math · Secondary 4 · Hard · R-formula

Write

5\cos\theta-12\sin\theta

in the form

R\cos(\theta+\alpha)

, where

R>0

and

0<\alpha<\tfrac{\pi}{2}

.

$13\cos(\theta+\alpha)$ , where $\cos\alpha=5/13$
$13\cos(\theta-\alpha)$ , where $\cos\alpha=5/13$
$13\cos(\theta+\alpha)$ , where $\cos\alpha=12/13$
$13\cos(\theta-\alpha)$ , where $\cos\alpha=12/13$

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