# Precalculus

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Can anyone help me with this question please!!

Show that
(cosh x)^2 - (sinh x)^2 = 1
for every real number x.

• Precalculus -

Expand and simplify using:
cosh(x)=(ex+e-x)/2
sinh(x)=(ex-e-x)/2
noting that ex * e-x=1

For the domain, since both ex and e-x have a domain of R, so the expression cosh(x)²-sinh(x)²=1
also has a domain of R, or (-∞,&infin).

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