Write the function in terms of its cofunction. Assume that any angle in which an unknown appears is an acute angle.
-$\cos 64 ^ { \circ }$
A) $\cos 154 ^ { \circ }$
B) $\sin 64 ^ { \circ }$
C) $\sin 26 ^ { \circ }$
D) $\sec 26 ^ { \circ }$

Question

Quizplus · Accepted Answer

The cofunction identity states that $\sin(\theta) = \cos(90^\circ - \theta)$. Therefore, $\cos(64^\circ) = \sin(90^\circ - 64^\circ) = \sin(26^\circ)$.

Write the Function in Terms of Its Cofunction cos⁡64∘\cos 64 ^ { \circ }cos64∘

Write the Function in Terms of Its Cofunction $\cos 64 ^ { \circ }$