Which properties belong to all isosceles triangles? Check all that apply.The base angles are congruent.All three angles are congruent.The two sides opposite the base angles are congruent.All three sides are congruent.The bisector of the vertex angle is the perpendicular bisector of the base.

An isosceles triangle has two congruent sides, so the sides opposite its two base angles are congruent (C). Those congruent sides also make the base angles congruent (A). The bisector of the vertex angle in an isosceles triangle divides the base at a right angle and into two equal parts, so it is the perpendicular bisector of the base (E). All three angles or all three sides are congruent only in an equilateral triangle, not every isosceles triangle.

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