Isosceles and Equilateral Triangles

Front

What is an isosceles triangle?

Back

An isosceles triangle is a triangle that has at least two sides of equal length and the angles opposite those sides are equal.

Front

What is an equilateral triangle?

Back

An equilateral triangle is a triangle in which all three sides are of equal length and all three angles are equal, each measuring 60°.

Front

If an isosceles triangle has a base angle of 40°, what is the vertex angle?

Back

The vertex angle is 100°.

Front

In an isosceles triangle, how do you find the vertex angle if the base angles are known?

Back

The vertex angle can be found using the formula: Vertex Angle = 180° - 2(Base Angle).

Front

What is the sum of the interior angles of a triangle?

Back

The sum of the interior angles of a triangle is always 180°.

Front

If two triangles are congruent, what can be said about their corresponding angles and sides?

Back

If two triangles are congruent, their corresponding angles are equal and their corresponding sides are equal in length.

Front

What does it mean for two triangles to be similar?

Back

Two triangles are similar if their corresponding angles are equal and their corresponding sides are in proportion.

Front

How can you determine if two triangles are congruent using the SSS criterion?

Back

Two triangles are congruent by the SSS (Side-Side-Side) criterion if all three sides of one triangle are equal to the three sides of another triangle.

Front

What is the relationship between the angles in an equilateral triangle?

Back

In an equilateral triangle, all three angles are equal, each measuring 60°.

Front

If ΔDEF ≅ ΔRST, what can be concluded about ∠T?

Back

∠T ≅ ∠F.