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## Homework Statement

Prove Sech^2(x) = 1 - tanh^2(x)

## Homework Equations

TanH(x) = (e^x - e^-x)/(e^x+e^-x)

CosH(x) = (e^x+e^-x)/2

SinH(x) = (e^x - e^-x)/2

## The Attempt at a Solution

SecH^2(x) = 1/cosh^2(x)

=1 / (e^x - e^-x)^2 / 4

=4/(e^x - e^-x)^2

This is where I am stuck. Any help is greatly appreciated. Thank you !