Question 952828
Show that (cosh x)^2 - (sinh x)^2= 1
for every real number x.
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{{{(e^x + e^(-x))^2/4 - (e^x - e^(-x))^2/4 = 1}}}
{{{(e^(2x) + e^(-2x) + 2)/4 - (e^(2x) - e^(-2x) - 2)/4 = 1}}}
{{{(e^(2x) + e^(-2x) + 2 - e^(2x) + e^(-2x) + 2)/4 = 1}}}
4/4 = 1