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In ∆ABC, point M is the midpoint of side BC. If AB2 + AC2 = 290 cm, AM = 8 cm, find BC. |
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Answer» In ∆ABC, point M is the midpoint of side BC. [Given] ∴ seg AM is the median. ∴ AB2 + AC2 = 2 AM2 + 2 MC2 [Apollonius theorem] ∴ 290 = 2 (8) + 2 MC2 ∴ 145 = 64 + MC2 [Dividing both sides by 2] ∴ MC2 = 145 – 64 ∴ MC2 = 81 ∴ MC = \(\sqrt {81}\) [Taking square root of both sides] MC = 9 cm Now, BC = 2 MC [M is the midpoint of BC] = 2 × 9 ∴ BC = 18 cm |
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