### Home > INT3 > Chapter 12 > Lesson 12.2.3 > Problem12-109

12-109.

Write each angle as the sum or difference of two special angles and then calculate the exact sine or cosine.

1. $\quad \operatorname { sin } ( \frac { 7 \pi } { 12 } )$

Refer to problem 12-108. Find a way to add or subtract two familiar angles from the unit circle to get the desired angle.
Then use the appropriate identity from the Math Notes in Lesson 12.2.3.

$\sin\left (\frac{\pi}{3}+\frac{\pi}{4} \right )=\frac{\sqrt{6}+\sqrt{2}}{4}$

1. $\quad \operatorname { cos } ( \frac { 11 \pi } { 12 } )$

Use the same method as part (a).