Step 1: Recall all the theorems of the circles


Step 2: Identify the appropriate theorem by observing the given diagram.

Step 3: Apply the appropriate theorem and calculate the unknown value

            NOTE: According to the theorem of chords of a circle, the angle subtended

                        at the center of the circle by an arc is twice the angle subtended by

                        it at any other point on the circumference.

                EXAMPLE: ∠POQ is equal to two times of ∠PRQ.

                                  Therefore, ∠POQ = 2 x ∠PRQ

                                                ⇒ ∠POQ = 2 x 620 = 1240