- (a) Use the definition of \(\sinh x\) in terms of exponentials to show that
$$\sinh 3 x \equiv 4 \sinh ^ { 3 } x + 3 \sinh x$$
(b) Hence determine the exact coordinates of the points of intersection of the curve with equation \(y = \sinh 3 x\) and the curve with equation \(y = 19 \sinh x\), giving your answers as simplified logarithms where necessary.