User:Hadseys/A Level maths

1. a) Use the definitions $$cosh x = \frac{1}{2}(e^x + e^-x)$$ and $$sin x = \frac{1}{2}(e^x - e^-x)$$ to show that $$cosh^2 x - sinh^2 x = 1$$

1. b) Express $$5 cosh^2 x + 3 sinh^2 x$$ in terms of $$cosh x$$