compund angle formula prob

Nov 2012
hello i am having trouble with a question here it is

use an appropriate compound angle formulae to express a a single trig formula than determine an exact formula for each

a) sin pi/4 cos pi/12 +cos pi/4 sin pi/12

so i got most of it i put it in to the fourmla sin(x+y)=sinxcosx+cosysinx

i solved for the right side and got square root of 3 over 2
but for the left side i am having trouble relating pi/12 to a special triangle as it is only 15
so far i am only able to do
sin pi/4 cos pi/12 + cos pi/4 sin pi/12
1/sq root of2 + blank+1/sq of root 2 + blank

as you can see i can solve the cos pi/12 and sin pi/12 if some one could please help me and show full steps as there is the same number for the diff compund formulas so i can see how to solve thos thank you
Dec 2011
Hint: sin(pi/12) = sqrt((1-cos(pi/6))/2)
Last edited:
Oct 2012
Hi Zxcismia,
your solution is perfect:
as you wrote.