Find the length of altitude AD of an isosceles ΔABC in which AB = AC = 2a units and BC = a units.

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Δ ABC is an isosceles triangle.


Also, AB = AC = 2a


The AD is the altitude. Therefore, D is the midpoint of BC.



ΔADB and ΔADC are right-angled triangles.


Applying Pythagoras theorem,


AB2 = BD2 + AD2





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