Question

Evaluate: sin(8pi/15)cos(pi/5) - cos(8pi/15)sin(pi/5)

Show solutions please. This isn't graded or anything, just doing some practice exercises so I can understand the lessons better.

Answer 1

its in the form of sinAcosB-cosAsinB=sin(A-B)
here
A=8pi/15
B=pi/5
(A-B)=(8pi/15)-(pi/5)
=pi/3=60degrees

so sin(A-B)=sin(pi/3)
final answer will be \[\sqrt{3}\div2\]