Write in terms of the cofunction of a complementary angle.
-$$\cos \frac { \pi } { 20 }$$
A) $\sin \frac { 19 \pi } { 20 }$

B) $\sec \frac { 19 \pi } { 20 }$

C) $\sin \frac { 9 \pi } { 20 }$

D) $\sec \frac { 9 \pi } { 20 }$

Question

Write in terms of the cofunction of a complementary angle.
-$$\cos \frac { \pi } { 20 }$$
A) $\sin \frac { 19 \pi } { 20 }$

B) $\sec \frac { 19 \pi } { 20 }$

C) $\sin \frac { 9 \pi } { 20 }$

D) $\sec \frac { 9 \pi } { 20 }$

Quizplus · Accepted Answer

The cofunction identity states that $\cos(\theta) = \sin(\frac{\pi}{2} - \theta)$. For $\theta = \frac{\pi}{20}$, the complementary angle is $\frac{\pi}{2} - \frac{\pi}{20} = \frac{9\pi}{20}$, so $\cos \frac{\pi}{20} = \sin \frac{9\pi}{20}$.

Write in Terms of the Cofunction of a Complementary Angle cos⁡π20\cos \frac { \pi } { 20 }cos20π​

Write in Terms of the Cofunction of a Complementary Angle $\cos \frac { \pi } { 20 }$