Math Help - Finding a differential.

1. Finding a differential.

i is sqrt(-1) and z is a complex number,d stand for differential
prove:if z-i=e^(it),then dz=ie^(it)dt

Differentiate both sides with respect to t... i is a constant.

please show steps because i forgot how to do differential

$\dfrac{d}{dx} e^{ax} = ae^{ax}$

It's an application of the chain rule and the special case of e.