Question

what is always true about the angles of an isosceles triangle?
all three angles are congruent.
at least two of the angles are congruent.
the vertex angle is a right angle.
the vertex angle is obtuse.

Explanation:

An isosceles triangle has at least two congruent sides (legs). By the Isosceles Triangle Theorem, the angles opposite those congruent sides (base angles) are congruent. So, at least two angles are congruent.

• All three angles congruent: This is for equilateral triangles (a special case of isosceles, but not always true for all isosceles).
• Vertex angle is a right angle: Only in right - isosceles triangles (not all isosceles).
• Vertex angle is obtuse: Only in some isosceles triangles (not all).

Answer:

At least two of the angles are congruent.