Question

Which characteristics will prove that ΔDEF is an acute, isosceles triangle?

Answer 1

Answer:

  a.  segment DE and segment EF are congruent to each other but not to segment DF, and their slopes are not related.

Step-by-step explanation:

In order for a triangle to be isosceles, two of the line segments must be congruent. (eliminates choices C and D)

If the slopes of the congruent segments are negative reciprocals of each other, the triangle is a right triangle, not an acute triangle. (eliminates choice B)

With choices B, C, D eliminated, we are left with choice A.

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However, that necessary description is not sufficient to constrain the triangle to be an acute triangle. In order for the triangle to be acute, the third side must be less than √2 times the length of either of the congruent sides.

The correct answer is "none of the above."