Let's draw a picture and see:

find the trig functions of angle  if the terminal side of  passes through the point (-12, 5).

Notice I changed the name of the angle from x to  because
x stands for the first coordinate of a point.  If you use x to refer
to the angle too, you will have a conflict of variables.  That's a
no-no.



Now we draw a perpendicular line down to the x-axis:



Next we cut off the green line beyond the right triangle, and label
it r.  We use the Pythagorean theorem to calculate r:










 

Edwin