I am self-studying A-levels pure maths and I need a little bit of help with understanding these questions.

Find, to 1 decimnal place, all values of z in the interval -180 <= z <= 180 satisfying:

(a) coz z deg (1 + sin z deg) = 0

In this questions, it's easy to guess that it must be at -90 or 90 but I don't understand how to solve the equation.

(b) (1 - tan z deg) sin z deg = 0

I am clueless on this one.

Ideas please? Perhaps could you help me find a place that better explains this?