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• #COROLLARY ISOSCELES TRIANGLE THEOREM HOW TO#

That means that the measure of angle 𝐴𝐷𝐶 is congruent to the measure of angle 𝐴𝐷𝐵. We can also write that 𝐴𝐶 is equal to 𝐴𝐵 because we know that the triangle is isosceles and the line segment 𝐴𝐷 is a shared side in the two triangles 𝐴𝐷𝐶 and 𝐴𝐷𝐵.Īnd as there are now three congruent pairs of sides, then we can say that triangle 𝐴𝐷𝐶 is congruent to triangle 𝐴𝐷𝐵 by the SSS, or side-side-side, congurrency criterion. We can therefore say that 𝐶𝐷 is congruent to 𝐵𝐷. The median of a triangle is a line segment joining a vertex to the midpoint of the opposite side and therefore bisecting that side. Let’s take this isosceles triangle 𝐴𝐵𝐶, and we draw the median from 𝐴 to create the point 𝐷. We can prove this corollary in the following way. This corollary states that the median of an isosceles triangle from the vertex angle bisects it and is perpendicular to the base. Let’s see the first of these corollaries. These corollaries will allow us to identify additional geometric properties about isosceles triangles. We will now consider a number of corollaries to these theorems.

That is, if two angles of a triangle are congruent, then the sides opposite those angles are also congruent. And the converse of this theorem is also true. And by this theorem, it means that they also have two congruent angles. So we know that isosceles triangles by definition have two congruent sides. The remaining angle in the isosceles triangle is referred to as the vertex angle. So knowing that the two sides are congruent means that in fact the two base angles are congruent. It is the isosceles triangle theorem, and it states that if two sides of a triangle are congruent, then the angles opposite those sides are congruent. Now, because isosceles triangles have two congruent sides, this leads us to an important angle property of isosceles triangles. The congruent sides are called the legs of the triangle and the third side is the base.

And when we are talking about isosceles triangles, we use two important terms. We can recall that an isosceles triangle is simply a triangle that has two congruent sides.

#COROLLARY ISOSCELES TRIANGLE THEOREM HOW TO#

In this video, we will learn how to use the corollaries of the isosceles triangle theorems to find missing lengths and angles in isosceles triangles.