What have you tried? You need to show an attempt at a solution before anyone can help you out. What trig identities do you know?
Wait. I'm just asking one question.
The trig identity I was trying to use was cos = sin (pi/2-theta).
I'm sorry, I haven't taken trig for along time and I'm just trying to brush up for my admissions test. I'm not too positive what it is asking when it states establish an identity. Am I suppose to prove it?