1.

In ∆ABC, point M is the midpoint of side BC. If AB2 + AC2 = 290 cm, AM = 8 cm, find BC.

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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