Originally Posted by

**kmjt** 12.a) Determine an exact value for sin 17pi/12.

b) Determine the answer to part a) using a different method.

So as of now I only know one way to do it.. which is using the compound angle formula. This is what I did:

sin(x+y) = sinxcosy+cosxsiny

sin(2pi/3 + 3pi/4) = sin(2pi/3)cos(3pi/4)+cos(2pi/3)sin(3pi/4)

=(sqr3/2)(-1/sqr2) + (-1/2)(1/sqr2)

=-sqr3/2sqr2 + -1/2sqr2

=-sqr3-1/2sqr2

This is the correct answer. Any ideas on what a second way of finding the exact value of sin 17pi/12 would be? The easier the better haha.

You can check the answer with your calculator:

Code:

>sin(17*pi/12)
-0.965926
>
>(sqrt(3)/2)*(-1/sqrt(2))+(-1/2)*(1/sqrt(2))
-0.965926
>

Your poor use of brackets makes it difficult to tell if you have simplified correctly.

For a second method use:

$\displaystyle \sin(17 \pi/12)=\sin(\pi +5\pi/12)=-\sin(5\pi/12)$

Now proceed as before.

CB