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Incircle area of a 16-16-24 isosceles triangle

Question

An isosceles triangle has sides 1616, 1616 and 2424. The biggest circle that fits inside it has area pπq\dfrac{p\pi}{q} with p/qp/q in lowest terms. Compute p+qp+q.

Short answer

151151. The height onto the base of 2424 is 162−122=47\sqrt{16^2-12^2}=4\sqrt7, so the area is 48748\sqrt7. Dividing by the semiperimeter 2828 gives inradius r=1277r=\tfrac{12\sqrt7}{7}, and πr2=144π7\pi r^2=\tfrac{144\pi}{7}, so p+q=151p+q=151.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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