I need help with this one and someone help me

Given: ac and db are diameters. m∠3=

The graph shows the distance y, in inches, a pendulum moves to the right (positive displacement) and to the left (negative displacement), for a given number of seconds x. how many seconds are required for the pendulum to move from its resting position and return? enter your answer in the box.

Place the following steps in order to complete the square and solve the quadratic equation,