In an equilateral triangle ABC, D is a point on side BC such that BC. Prove that 9AD2 = 7AB2.
Asked by Topperlearning User | 4th Jun, 2014, 01:23: PM
Draw AP BC.
Since ABC is equilateral and AP BC,
BP = PC = BC = AB
Using Pythagoras theorem in ABP,
AP2 + BP2 = AB2
AP2 = AB2 - BP2 = AB2 - = … (1)
Using Pythagoras theorem in ADP,
AD2 = AP2 + DP2
= AB2 + (BP - BD)2
= AB2 +
36AD2 = 28AB2
9AD2 = 7AB2
Answered by | 4th Jun, 2014, 03:23: PM
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