Trig
posted by Melody .
Are any of these three problems identities?
1. Cos^2xsin^2x=12sin^2x
2. Sinxsecx=cosxcscx
3. Sec^4xtan^4/sec^2x=1+sin^2x
If so, how can you conclude that any of them are identities?

Identities are trigonometric equations that must be valid for any value of the angle. That is only true for the first equation.