In the diagram, POQ is the diameter of the circle centre O. Calculate ∠QRS
Attached Figure / Diagram
A
35o
B
70o
C
100o
D
125o
Verified Correct Answer: D.
Step-by-Step Mathematical Solution
∠PSQ = 90^\circ (angle in a semi-circle)
(when SR is joined to SP)
∠SPQ = 180 – (90+35) = 180 – 125 = 55^\circ
∠QRS + ∠SPQ = 180^\circ (opposite angles in a cyclic quad is supplementary)
∠QRS = 180^\circ - 55^\circ
= 125^\circ
Source: Myschool Past Questions Archive (Record #26629)