Question 241762
You don't need to use the double angle identities. Take note that *[Tex \LARGE \frac{3\pi}{12}=\frac{\pi}{4}]. 



So *[Tex \LARGE \sin\left(\frac{3\pi}{12}\right)=\sin\left(\frac{\pi}{4}\right)=\frac{\sqrt{2}}{2}] using the unit circle.