# One more trig identity

## Homework Statement

I'm finally starting to understand proving trig identities, but I have just one more that I can't seem to figure out.

secx - tanxsinx = cosx

N/A

## The Attempt at a Solution

Well first, I multiplied the tanx and sinx and came up with sin2x / cosx
Now I'm stuck. I'm trying to do 1/cosx - sin2x / cosx
Would the GCF be (cosx)(cosx) or just cosx, I'm drawing a blank here. I'm debating whether or not to change the sin2x to 1 - cos2x, but even if I do, I can't figure out how that would simplify to just cosx

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Cyosis
Homework Helper
You're almost there$$\frac{1}{\cos x}-\frac{\sin^2x}{\cos x}=\frac{1}{\cos x}(1-\sin^2x)$$. You should notice something very familiar now.

So would it simplify to cos2x / cosx, which would then simplify to cosx for my answer?

Cyosis
Homework Helper
Yep it's that easy!