My professor taught us to solve few questions of sine by doing this. I don't understand what he did to get the answer. I can get the answer without doing any steps but I need to understand how he has done it.
= sin (3pi/2 + 8pi/2)
= sin (3pi/2 + 4pi)
= sin (3pi/2) <--- i don't know why 4pi just disappears.
Can I also get a different example with cosine and a negative sign so I can understand better. Thanks.