## Trigonometry (11th Edition) Clone

$\theta = 45^{\circ}$ or $315^{\circ}$
1. Since $cos\theta$ is positive, $\theta$ must be in quadrant I or IV. 2. The reference angles is $45^{\circ}$. The other angle in IV quadrant must be : $360^{\circ}-45^{\circ}=315^{\circ}$