Question

Find cos8pi/3 i forgot how to do this :/

Answer 1

do you know what cos pi/3 is?

Answer 2

1/2?

Answer 3

If you do, then ans is negative of this. Why?

Answer 4

But how do i solve problems like this? Like : sin5pi/2

Answer 5

so you know that 5pi/2 goes around and stops, where, pi/2 is 90, 2 pi/2 is 180, 3 pi/2 is 270, 4 pi/2 is back to 0 and then 5 pi/2 is 90 again. So you have 5 pi /2, which is greater than 2pi, right? So you start all over after 5 pi/2 - 2 pi = pi/2