In Δ A B C ─
Sides: A B = c , C A = b , B C = a ;
Medians: A D = d , B E = e , C F = f .
Given a > b > c , which of the medians is the largest?
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Why? Median doesn't mean the height of the small triangle.
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therefore the shorter the median the larger the sine and so the side opposed to it.
From comparison among the equal areas of triangle AMB = 2/9 d e sin(AMB) ; to area AMC = 2/9 d f sin(AMC) and to the area CMA = 2/9 f e sin(CMA). since d < e < f therefore
I will apply the Apollonius' Theorem .
By applying Apollonius' Theorem , we can have─
c 2 + b 2 = 2 ( d 2 + ( 2 a ) 2 )
⟹ c 2 + b 2 = 2 ( d 2 + 4 a 2 )
⟹ c 2 + b 2 = 2 × 4 4 d 2 + a 2
⟹ c 2 + b 2 = 2 4 d 2 + a 2
⟹ 4 d 2 = 2 ( b 2 + c 2 ) − a 2
⟹ 4 d 2 = 2 ( a 2 + b 2 + c 2 ) − 3 a 2 … … … ( I ) .
Similarly,
4 e 2 = 2 ( a 2 + b 2 + c 2 ) − 3 b 2 … … … ( I I ) .
4 f 2 = 2 ( a 2 + b 2 + c 2 ) − 3 c 2 … … … ( I I I ) .
As a > b > c , we can conclude from ( I ) , ( I I ) and ( I I I ) that
4 d 2 < 4 e 2 < 4 f 2
⟹ d < e < f .
Yes, The larger side supports the smaller median in a triangle . So, f is the answer.
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Solution is obvious naming M as the point where the three medians meet. The three triangles AMB, BMC, CMA have same area therefore the smallest side base c AB in our case has to have the largest median CF.
The picture below will help to visualize the proof, just comparing areas of colored paralellograms.