Question

Can someone explain this to me... Why when these are ^2'd does a random +/- 2 appear in the middle?

cosh(x) = (e^(x) + e^(-x)) / 2
sinh(x) = (e^(x) - e^(-x)) / 2

cosh²(x) = (e^(2x) + 2 + e^(-2x)) / 4
sinh²(x) = (e^(2x) - 2 + e^(-2x)) / 4

cosh²(x) - sinh²(x)
= (e^(2x) + 2 + e^(-2x))/4 - (e^(2x) - 2 + e^(-2x)) / 4
= (e^(2x) + 2 + e^(-2x) - e^(2x) + 2 - e^(-2x)) / 4
= 4/4
= 1

Answer 1

no one?