Past exam of the mathematical methods I course of the University of Oxford / 2016 / 2 / Solution

The complex sine identity isIt follows either from the exponential definition of sine or its addition formula, using $\sin (iy)=i\sinh y$ and $\cos (iy)=\cosh y$. ConsequentlyThe angles $2$ and $3$ in these functions are dimensionless; the real trigonometric argument is measured in radians.