This question is in the exercises associated with reference angles. I understand the reference angle part, but there is a question, which I don't know how to work with or without a calculator.

Approximate to three decimal places:

a) sin 73deg 20'

b) cos 0.68

The answers are a) .958 and b) .778 though I don't know where to start. I don't know what the 20' means either.

I looked through the web for some info and the purplemath sections, but I can't get it to work out