## Are base angles in an isosceles triangle always congruent?

An isosceles triangle is a triangle that has at least two congruent sides. The congruent sides of the isosceles triangle are called the legs. One of the important properties of isosceles triangles is that their base angles are always congruent. This is called the Base Angles Theorem.

## Why are the base angles of an isosceles triangle equal?

As in any isosceles triangle two of its sides are always congruent and also angles opposite to congruent sides are congruent. Hence the base angles of an isosceles triangle are congruent. Yes, if a triangle is isosceles, then base angles are congruent. Let’s prove that.

**What angles are congruent in the isosceles triangle?**

Isosceles triangles have at least two congruent sides and at least two congruent angles. The congruent sides, called legs, form the vertex angle. The other two congruent angles are the base angles.

**What theorem is used to determine if the base angles of a triangle are congruent?**

Angles:

Right Angles | All right angles are congruent. |
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Base Angle Theorem (Isosceles Triangle) | If two sides of a triangle are congruent, the angles opposite these sides are congruent. |

Base Angle Converse (Isosceles Triangle) | If two angles of a triangle are congruent, the sides opposite these angles are congruent. |

### Are the base angles of an isosceles trapezoid congruent?

Univ. An isosceles trapezoid has two congruent legs and one pair of parallel sides. The base angles are congruent to one another, and by same side interior angles, the upper angles are supplementary to the respective base angles, meaning that they are both 180° – (the measure of the base angle).

### What formula do you use to prove a triangle is isosceles?

Theorem 2: Sides opposite to the equal angles of a triangle are equal. Proof: In a triangle ABC, base angles are equal and we need to prove that AC = BC or ∆ABC is an isosceles triangle.

**How do you prove a triangle is isosceles?**

Hence proved. Theorem 2: Sides opposite to the equal angles of a triangle are equal. Proof: In a triangle ABC, base angles are equal and we need to prove that AC = BC or ∆ABC is an isosceles triangle….Isosceles Triangle Theorems and Proofs.

MATHS Related Links | |
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Reflection Symmetry | Surface Area Of A Cone |

**How do you prove that a triangle is isosceles?**

Explanation: One way of proving that it is an isosceles triangle is by calculating the length of each side since two sides of equal lengths means that it is an isosceles triangle.

## How do you prove it is an isosceles triangle?

If a triangle has two congruent angles, then the sides opposite those angles are congruent. In other words, iso-angular triangles are iso-lateral (isosceles). This is the converse of the isosceles triangle theorem.