# compund angle formula prob

• Nov 3rd 2012, 05:56 AM
zycismia
compund angle formula prob
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
• Nov 3rd 2012, 07:01 AM
alphabeta89
Re: compund angle formula prob
Hint: sin(pi/12) = sqrt((1-cos(pi/6))/2)
• Nov 5th 2012, 08:37 AM
StefanTM
Re: compund angle formula prob
Hi Zxcismia,