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**Animesh****Guest**

Tangents at the points P and Q on a circle meet at R. If PQ = 6 cm and PR = 5 cm find the radius of the circle

**alter ego****Member**- Registered: 2012-03-30
- Posts: 19

Hi Animesh,

Join R to the centre, O, of the circle. Triangles OPR and OQR are congruent as they have a 90 degree angle and one side in common plus equal radii, OP and OQ.

So OR is a line of symmetry . If OR crosses PQ at S then SP = 3,so RS = 4 by Pythagoras. If you let OS = x and radius = r you can form two equations in r and x by Pythagoras on OPR and on OPS.

It's easier to eliminate r and find x. Then find r.

Alter

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