Question

the vertices of triangle PQR are P(3,9), Q(-6,-2) and R(-1,3). Determine the measures of the interior angles of triangle PQR

Answer 1

Start off by finding the length of each of the three sides. You can use the distance formula for the distance between two points \((x_1,y_1)\) and \((x_2,y_2)\)
\[d = \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}\]

Answer 2

have you covered the Law of Cosines yet?