1971 Canadian MO Problems/Problem 1


$DEB$ is a chord of a circle such that $DE=3$ and $EB=5 .$ Let $O$ be the center of the circle. Join $OE$ and extend $OE$ to cut the circle at $C.$ Given $EC=1,$ find the radius of the circle.

CanadianMO 1971-1.jpg


First, extend $CO$ to meet the circle at $P.$ Let the radius be $r.$ Applying power of a point, $(EP)(CE)=(BE)(ED)$ and $2r-1=15.$ Hence, $r=8.$

See Also

1971 Canadian MO (Problems)
Preceded by
First Question
1 2 3 4 5 6 7 8 Followed by
Problem 2