Find a cofunction with the same value as the given expression.
-$\sin \frac { \pi } { 18 }$
A) $\cos \frac { 4 \pi } { 9 }$
B) $\sin \frac { 4 \pi } { 9 }$
C) $\cos \frac { \pi } { 18 }$
D) $\sin \frac { \pi } { 18 }$

Question

Quizplus · Accepted Answer

Cofunction identities state that $\sin(\theta) = \cos(\frac{\pi}{2} - \theta)$. Therefore, $\sin(\frac{\pi}{18}) = \cos(\frac{\pi}{2} - \frac{\pi}{18}) = \cos(\frac{9\pi - \pi}{18}) = \cos(\frac{8\pi}{18}) = \cos(\frac{4\pi}{9})$.

Find a Cofunction with the Same Value as the Given sin⁡π18\sin \frac { \pi } { 18 }sin18π​

Find a Cofunction with the Same Value as the Given $\sin \frac { \pi } { 18 }$