CBSE Class 9 Answered

<div>AD,BE and CF,the medians of triangle ABC are equal.then prove that triangle ABC is a equilateral triangle.</div>

Asked by abinash.gupta003 | 26 Aug, 2016, 03:46: PM

Expert Answer

begin mathsize 14px style Let space the space emdians space intersect space at space point space straight M. rightwards double arrow straight M space is space centroid space of space triangle space ABC. Now comma space centroid space divides space the space median space in space teh space ratio space 2 space colon space 1 Thus comma space we space have AM space colon space MD space equals BM space colon space ME space equals CM space colon space MF space equals space 2 space colon space 1 space space The space question space says space that space the space medians space are space equal space in space length. space So space let space us space say space AM space equals space BM space equals space CM space equals space 2 space units space and space MD space equals space ME space equals space MF space equals space 1 space unit Now space consider space triangle CDM space and space triangle AFM comma CM space equals space AM FM space equals space MD angle AMF space equals space angle CMD rightwards double arrow triangle CDM space approximately equal to triangle CMD rightwards double arrow AF space equals space CD But space straight F space is space the space mid minus point space of space AB comma space rightwards double arrow AF space equals space FB rightwards double arrow AF space equals space FB space equals space BD space equals space CD Hence comma space AF space plus space FB space equals space BD space plus space CD rightwards double arrow AB space equals space BC Similarly comma space we space can space show space BC space equals space AC space and space space hence space AB space equals space BC space equals space AC rightwards double arrow ABC space is space an space equilateral space triangle. end style

Answered by Rashmi Khot | 26 Aug, 2016, 05:44: PM

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