Question

Given that sinΘ = 1/2 and that Θ lies in quadrant II, determine the value of cosΘ.

Answer 1

With $\theta$ in quadrant II, we expect to have $\cos\theta$. Then

$\cos^2\theta+\sin^2\theta=1\implies\cos\theta=-\sqrt{1-\sin^2\theta}$

$\implies\cos\theta=-\dfrac{\sqrt3}2$