In the diagram above, O is the centre of the circle, POM is a diameter, and \(\angle\) MNQ = 42º. Calculate \(\angle\) QMP.
Attached Figure / Diagram
A
42º
B
48º
C
132º
D
138º
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
POM is a diameter, so arc MP (lower semicircle via Q) = 180^\circ.
∠MNQ = 42^\circ is an inscribed angle subtending arc MQ.
Therefore, arc MQ = 2 \times 42^\circ = 84^\circ
Arc MQ + arc QP = lower semicircle:
arc QP = 180^\circ − 84^\circ = 96^\circ
- ∠QMP is an inscribed angle subtending arc QP.
Therefore, ∠QMP = \(\frac{1}{2}\) \times 96^\circ = 48^\circ.
(Alternatively: in right triangle PQM, ∠PQM = 90^\circ (angle in a semicircle), so the angles at M and P sum to 90^\circ; the arc method directly gives the result.)
Source: Myschool Past Questions Archive (Record #76318)