Posted by **John** on Tuesday, November 6, 2012 at 2:04pm.

How to prove tan4x = 1-8 sin squared of cos squared of x

- Pre Calc -
**Steve**, Tuesday, November 6, 2012 at 2:35pm
I don't think you really meant

tan(4x) = 1 - sin^2(cos^2(x)), so do you mean

tan 4x = 1 - 8 sin^2 x cos^2 x?

Let's see.

8sin^2 x cos^2 x = 2*sin^2(2x))

tan(4x) =? 1 - 2sin^2(2x)

Naah. Check your problem again.

However, cos(4x) = 1 - 2sin^2(2x))

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