solve using the compound angle formula: sin(17pi/12)

[M-D]

i've got this question which must be solved without a calculator. the questions is: sin(17pi/12). this is what i have done:

sin(17pi/12)=sin[17(pi/12)]=sin[17(pi/3-pi/4)]

i don't know what to do next.
could you please guide me on what to do. it says in the question that i am to find the exact value using the compound angle formula.
thanks

[thushan]

you know angle 17pi/12 = -5pi/12 (they are the same angle)

so sin(17pi/12) = sin(-5pi/12) = -sin(5pi/12) = -sin(pi/4 + pi/6)

Go from there.

[M-D]

thanks Rexxy. i googled the question and found another way of computing it. 17pi/12 is the same as 9pi/12+8pi/12 and from there you just use the compound angle formula.