Write in terms of the cofunction of a complementary angle.
-$$\sin \frac { \pi } { 9 }$$
A) $\csc \frac { 7 \pi } { 18 }$
B) $\cos \frac { 7 \pi } { 18 }$
C) $\cos \frac { 8 \pi } { 9 }$
D) $\csc \frac { 8 \pi } { 9 }$

Question

Quizplus · Accepted Answer

The cofunction identity states that $\sin(\theta) = \cos(\frac{\pi}{2} - \theta)$. For $\sin(\frac{\pi}{9})$, the complementary angle is $\frac{\pi}{2} - \frac{\pi}{9} = \frac{7\pi}{18}$, so the correct expression is $\cos(\frac{7\pi}{18})$.

Write in Terms of the Cofunction of a Complementary Angle sin⁡π9\sin \frac { \pi } { 9 }sin9π​

Write in Terms of the Cofunction of a Complementary Angle $\sin \frac { \pi } { 9 }$