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Semi circle in a triangle
Permanent link to this puzzle: mscroggs.co.uk/puzzles/32
Source: UKMT Pink Kangaroo 2012
This right-angled triangle above has sides of lengths 12cm, 5cm and 13cm. The diameter of the semicircle lies on the 12cm side and the 13cm side is a tangent to the circle. What is the radius of the semi circle?