Olympiad workbookIOQMCircle
Let ₁ be a circle with centre O and let AB be diameter of ₁ . Let P be a point on the segment OB different from O . Suppose another circle ₂ with centre P lies in the interior of ₁ . Tangents are drawn from A and B to the circle ₂ intersecting ₁ again at A ₁ and B ₁ respectively such that A ₁ and B₁ are on the opposite sides of A B . Given that A₁ B=5, A B₁=15 and O P=10 , find the radius of ₁ .
Correct answer
20
Step-by-step solution
aligned & r₁ r+10 = 5 2 r & r₁ r-10 = 15 2 r & r-10 r+10 = 1 3 & 3 r-30=r+10 & 2 r=40 & r=20 aligned