Can somebody help me with this question? (Calculus)

Alex drew a circle with right triangle prq inscribed in it, as shown below: the figure shows a circle with points p, q, and r on it forming an inscribed triangle. side pq is a chord through the center and angle r is a right angle. arc qr measures 80 degrees.

Solve 2x+y=3 x+y=5 in substitution method

If value of cos330° is √3/2 then find tan165°.