JAMB 2014 · UTME · Q37

If $\sin\theta = \frac{12}{13}$ ( $\theta$ acute), find the value of $1 + \cos\theta$ .

Worked solution (try it first)

$\sin\theta = \frac{12}{13}$ , so draw a right-angled triangle with opposite side 12 and hypotenuse 13.
Pythagoras gives the adjacent side $\sqrt{169 - 144} = 5$ .
So $\cos\theta = \frac{5}{13}$ .
Add 1: $1 + \frac{5}{13} = \frac{18}{13}$ , option C.