1999 AHSME Problems/Problem 16
Problem
What is the radius of a circle inscribed in a rhombus with diagonals of length and ?
Solution
Let and be the lengths of the diagonals, the side, and the radius of the inscribed circle.
Using Pythagorean theorem we can compute .
We can now express the area of the rhombus in two different ways: as , and as . Solving for we get .
(The first formula computes the area as one half of the circumscribed rectangle whose sides are parallel to the diagonals. The second one comes from the fact that we can divide the rhombus into equal triangles, and in those the height on the side is equal to . See pictures below.)
See also
1999 AHSME (Problems • Answer Key • Resources) | ||
Preceded by Problem 15 |
Followed by Problem 17 | |
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