I have a question I'm having a bit of trouble with lads,

Determine the exact values for the 6 trig ratios Θ(theta) lies in the standard position with its terminal arm passing through the point P(-3,-5).

I know I'm supposed to find Sin, Cos, Tan, Csc, Sec, and Cot, but how do I find the radian measure so I can do so?

If anyone can help it would really be great, thanks so much!