We continued discussion of the function exp(z). We proved it satisfies
exp(z)exp(z') = exp(z+z'), which we used to use the alternate form:
exp(z)= e^z. Using this function we defined the trig functions:
cos(z), sin(z) and tan(z). Others such as cot(z), sec(z) and cosec(z)
were left to exercises. We derived the form of the derivatives of
cos(z) and sin(z), and derived analogous forms of some trig identities
familiar from when the variable is real. We determined for which z
cos(z)=0, which are where tan(z) is not defined. We also showed that
|cos(x,y)| grows like e^y as |y| gets large, for any x.

HW: sections 29,34