Question 583206: In the grid below, JKL is an isosceles triangle. What theorem leads to the conclusion that the triangle is not a right triangle?
Answer by richard1234(7193)   (Show Source):
You can put this solution on YOUR website! Isosceles triangles can indeed be right triangles, as long as the angles are 45, 45, 90.
Otherwise, any other theorem can disprove the statement that JKL is a right triangle, even the law of cosines.
Suppose that a,b,c are the sides, and c is the longest side. Then
The triangle is a right triangle if and only if cos C = 0, or C = 90. All other triangles cannot be right triangles.
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