Question

(cosh^2(3t))-(sinh^2(3t))

Answer 1

1

Answer 2

The question used hyperbolic cosine and sine functions.

Answer 3

Jm... In my opinion, I think Weeku-san is correct... Because these are hyperbolic functions and not the normal trigo function.
So
cosh^2 x + sinh^2 x = cosh2x
cosh^2 x - sinh^2 x = 1