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43. Bl and CMare medians of a triangle ABC right angled at A.Prove that 4(BL2+CMF) 5 BC2

Answer»

Given : ABC right angle triangle at A where BL and CM are the medians

To prove : 4(BL^2 + CM^2)=5BC^2

Proof :Since BL is the median

AL=CL=1/2 AC .............(1)

Similarly CM is the median

AM = MB = 1/2 AB .......)

In triangle ABC

BC^2 = AB^2 + AC^2

In triangle BAL

BL^2 =AB^2 +AL^2

BL^2 =AB^2 +(AC/2)^2

On further little solving steps

4BL^2 =4AB^2 +AC^2

Then in triangle MAC

CM^2 =AM^2 +AC^2

Doing same process here We get

4CM^2 =AB^2 +4AC^2



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