find the angles of the triangle formed by the points P(2,-2,5), Q(2,1,7) and R(7,6,-10)

do i use the dot product for this? which pairs would i use? does anyone know how to do this?

I got the following angles, are these right?

between P & Q = 28.8 degrees

" Q & R = 120 degrees

" P & R = 127.9 degrees