Math CentralQuandaries & Queries


brian, a student:

Three circles with radii 3,4 and 5 touch each other. The circles are tangent to each other. What is the area of the triangle formed by the centers of the circles?

Hi Brian.

One side must be 3+4 units long, another side must be 4+5 units long and the last side must be 3+5 units long.

Thus you know the lengths of all the sides of the triangle, so you can use Heron's Formula to calculate its area.

Stephen La Rocque

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