Finding area using similarity and congruence | Similarity | Geometry | Khan Academy

Example of using similarity and congruence to find the area of a triangle

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[onesandzeroes]

The whole calculation of the left side is superfluous as an isosceles triangle has by definition two congruent halves on both sides of its height.

[ElectricPeaPlayz]

Please make another video, and can it have some features that the questions do? I don’t see this

[Nmi]

@ricestube, yes, you can, but you have to base on the rule that "height which is drawn from the vertex angle to the base is also bisector and median in isosceles triangle".

[trna]

after finding DF, we could also subtract the area of smaller triangle from the larger triangle and multiply the result by 2 . 

[Nmi]

Do you know one rule about isosceles triangle? This rule says that height which is drawn from the vertex angle to the base is also bisector and median in isosceles triangle. I don't understand why couldn't you apply this rule here. Does it really need to prove the similarity or congruency of the bunch of triangles?

[shashikalakc]

This is actually a lil bit complex for me!

[ajinkyakarnik]

ur doing it in a very long way
we cud use the iso trianglr property that the median OR altitude bisects the base .... and we can easily prove that 3pairs of triangles are eqaul to be exact...