In Fig. 6.11, OP, OQ, OR and OS are four rays. Prove that `angle POQ + angle QOR + angle SOR + angle POS = 360^@`.

In Fig 7.51, PR > PQ and PS bisects angle QPR . Prove that angle PSR > angle PSQ .

In Fig. 6.15, angle PQR = angle PRQ , then prove that angle PQS = angle PRT .

Similarly we can prove that angle 2 = angle 4

Prove that complement of an angle is an acute angles.

Prove that angle in a semi-circle is right angle.

In Fig. 7.49, angle B

Prove that supplementary of an angle is an obtuse angles.

In Fig. 6.42, if lines PQ and RS intersect at point T, such that angle PRT = 40^@, angle RPT = 95^@ and angle TSQ = 75^@ , find angle SQT .