How to decide which sides is the base of isosceles triangle?

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When the Gmat mentions that ABC is isoscelens triangle, How to decide which sides is the base of isosceles triangle? Or we can not make a conclusion?

Thanks for your help

[GMATGuruNY]

Any side of a triangle can be deemed the base, and each base has a corresponding height.
For practice with this concept, check here:

https://www.beatthegmat.com/geometry-hel ... 17047.html
https://www.beatthegmat.com/geometry-t271788.html
https://www.beatthegmat.com/need-to-unde ... 68314.html

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Hi iambillgate2,

You mentioned Isosceles triangles specifically, so when you say "the base", do you mean "the side that does NOT match the other 2 sides?"

An Isosceles triangle does not necessarily "point up", so you have to be open to the idea that the base of the triangle is one of the 2 matching sides.

When a GMAT question mentions an Isosceles triangle, it may tell you which 2 sides are the Isosceles sides, but it may try to test your understanding of Isosceles triangles by giving you OTHER pieces of information (e.g. angles, perimeter/area, etc.) to see if you can figure out which 2 sides are Isosceles.

GMAT assassins aren't born, they're made,
Rich

[GMATinsight]

When the Gmat mentions that ABC is isoscelens triangle, How to decide which sides is the base of isosceles triangle? Or we can not make a conclusion?

Thanks for your help

CONCEPT : Any Side of the triangle can be considered as Base and for a chosen base the height is the perpendicular distance between the base and the third vertex of the Triangle