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PA and PB are tangents from a point P to a circle. If angle APB = 90 degrees, the radius and PA are related by
APA = r
BPA = r (square root of 2)
CPA = 2 r
DPA = r/2
Answer & Solution
Correct answer: A. PA = r
1. In quadrilateral OAPB, all four angles: OAP = OBP = 90, APB = 90, AOB = 90.
2. OAPB is a square with side r and side PA.
3. Hence PA = r.
_Source: NCERT Class 10 Mathematics, Ch 10 "Circles", §10.3_
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