Understanding Isosceles Triangles

The video tutorial explains the properties of isosceles triangles, focusing on the vertex angle formed between the two congruent sides. It demonstrates how to calculate the base angles when the vertex angle is known and vice versa. The tutorial provides examples to illustrate these calculations, emphasizing the congruency of the base angles and the sum of angles in a triangle being 180 degrees.

What is a defining characteristic of an isosceles triangle?

• All angles are equal.

• It has no equal sides.

• It has two congruent sides.

• All sides are different lengths.

Which of the following can an isosceles triangle also be?

• Scalene triangle

• Right triangle

• Equilateral triangle

• Obtuse triangle

Where is the vertex angle located in an isosceles triangle?

• Adjacent to the base angles

• Between the two congruent sides

• At the base of the triangle

• Opposite the longest side

If the vertex angle of an isosceles triangle is 110°, what is the measure of each base angle?

• 70°

• 55°

• 45°

• 35°

What is the sum of all angles in any triangle?

• 90°

• 180°

• 360°

• 270°

If one base angle of an isosceles triangle is 70°, what is the measure of the vertex angle?

• 70°

• 60°

• 40°

• 80°

In an isosceles triangle, if the base angles are equal, what can be said about the sides opposite these angles?

• They are congruent.

• They form a right angle.

• They are different in length.

• They are parallel.

How do you find the vertex angle if you know one base angle in an isosceles triangle?

• Subtract the base angle from 180°

• Add the base angle to 180°

• Divide the base angle by 2

• Subtract twice the base angle from 180°

What is the relationship between the base angles in an isosceles triangle?

• They are complementary.

• They are unequal.

• They are supplementary.

• They are congruent.

If the vertex angle is 40°, what is the measure of each base angle in an isosceles triangle?

• 50°

• 70°

• 80°

• 60°