### Home > CCA2 > Chapter 12 > Lesson 12.2.3 > Problem12-131

12-131.

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

1. $\sin\frac{7\pi}{12}$

What two special angles have a sum of $\frac { 7 \pi } { 12 }$$\sin\left(\frac{\pi}{3}+\frac{\pi}{4}\right)$

Now find the exact value of sine.

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

1. $\cos\frac{11\pi}{12}$

Use the same method as part (a).