Assertion (A): In the given figure, If O is the centre of the circle and AC is the diameter with ∠APB=120∘, then ∠BQC=150∘.
Reason (R): In a cyclic quadrilateral, the sum of opposite angles is 180∘.
Which of the following is true?
(A) is true and (R) is the correct explanation of (A)
Given, ∠APB=120∘
In cyclic quadrilateral ACBP,
∠APB+∠ACB=180∘⇒120∘+∠ACB=180∘⇒∠ACB=60∘
Also, ∠ABC=90∘ [angle in a semi circle]
∴InΔABC,∠BAC+∠BCA+∠ABC=180∘⇒∠BAC+60∘+90∘=180∘⇒∠BAC=30∘
Again, in cyclic quadrilateral ACQB,
∠CAB+∠CQB=180∘⇒30∘+∠CQB=180∘∴∠CQB=150∘
Reason (R)True