If a data sufficiency question about triangles asks whether a triangle is isosceles and in one of its two provisions mentions that two sides are equal, should we assume that the third side is unequal to the first two? In other words, the question is framed as follows:
Is the triangle in the attached picture isosceles?
1. a = b
2. c <> b
My answer would be E because a = b does not preclude b = c and hence that the triangle is equilateral. Though I agree that all equilateral triangles are isosceles in a sense, I do not assume GMAT will accept that 'sense.
Even if you consider that b could be equal to c, 2nd statement specifies that it ain't. Using both statements, we can definitely conclude that the triangle is an isosceles. But, I believe the answer should be A. Please refute if others don't agree.
Is this an official Data Sufficiency question?
If yes, "A" should be sufficient.
I believe an equilateral triangle is a special type of isosceles. I am not 100% sure though.
Square is special rectangle
Square is special rhombus.
There may be more such cases.
I get a feeling that this question is meant more for the main Math forum
(Intellectual Discussion) than an official "Data Sufficiency" question.
What do you say?
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