Thread: Trig inequality.

I'm trying to show that

5+8cos\theta+4cos2\theta+cos3\theta\geq0

but keep going around in circles.

Can anybody take a stab at it?

Uhm, what don't you know? Also, what have you tried and didn't work?

Try to use and .

Originally Posted by Cairo

I'm trying to show that

5+8cos\theta+4cos2\theta+cos3\theta\geq0

but keep going around in circles.

Can anybody take a stab at it?

A start would probably be to express and in terms of .