# Trig angle Formulas

#### carich4

Hey,
I am confused as to how to break down this question.

"Evaluate using formulas developed in this section."
a) sin 11pi/12

the formulas are the addition and subtraction as well as double angle formulas.
i know that 11pi/12 = pi/3 + pi/4 + pi/4 + pi/6 but am not sure how to turn it into a formula.

#### skeeter

MHF Helper
$\sin\left(\dfrac{11\pi}{12}\right) = \sin\left(\dfrac{3\pi}{4}+\dfrac{\pi}{6}\right)$

you should be familiar with the sine sum identity which you can use to evaluate ...

$\sin(a+b) = \sin{a}\cos{b}+\cos{a}\sin{b}$