I need help doing this

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.

Given: m∠ adb = m∠cdb ad ≅ dc prove: m∠ bac = m∠bca lol

What does independent variable and dependent variable mean in math?