We know that two circles will congruent if they have equal radii
From the figure, we know that if two chords are equal then the corresponding arcs are congruent
We know that PQ is the common chord in both the circles
So their corresponding arcs are equal
It can be written as
Arc PCQ=arc PDQ
We know that the congruent arcs have the same degree
So we get
∠QAP=∠QBP
We know that the base angles of an isosceles triangle are equal
So we get
QA=AB
Therefore, it is proved that QA=QB
13. Two equal circles intersect in P and Q. A straight line through P meets the circles in A and B. Prove that QA = QB.
Let C (O, r) and C(O', r) be two equal circles. clearly, C(O, r) ≅ C(O', r).
Since PQ is a common chord of two congruent circles.Therefore,arc PCQ = arc PDQ
⇒ ∠ QAP = ∠ QBP
Thus, in ΔQAB, we have∠ QAP = ∠ QBP⇒ QA = QB
Hence proved.
Two equal circles intersect in P and Q. A straight line through P meets the circles in A and B. Prove that QA = QB.
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