Understanding Isosceles Triangles

The video tutorial introduces isosceles triangles, explaining their properties, such as having two congruent sides or angles. It discusses how to identify these triangles by their sides and angles, and provides rules for understanding their characteristics. The tutorial also includes a practical example of calculating unknown angles in an isosceles triangle using known measures, emphasizing the concept of congruent base angles.

What is a defining characteristic of an isosceles triangle?

• It has three congruent sides.

• It has two congruent sides.

• All sides are different lengths.

• All angles are different.

Tags

CCSS.2.G.A.1

How many congruent sides does an isosceles triangle have?

• Three

• Two

• None

• One

In an isosceles triangle, if two sides are marked congruent, what can be said about the angles opposite these sides?

• They are different.

• They are congruent.

• They are complementary.

• They are supplementary.

Which of the following is true about the angles in an isosceles triangle?

• All angles are equal.

• One angle is 90 degrees.

• Two angles are congruent.

• All angles are different.

Tags

CCSS.8.G.A.5

In a right isosceles triangle, what is the measure of the two congruent angles?

• 60 degrees

• 30 degrees

• 90 degrees

• 45 degrees

Tags

CCSS.4.G.A.2

If two angles in a triangle are congruent, what type of triangle is it?

• Equilateral

• Isosceles

• Scalene

• Right

Tags

CCSS.8.G.A.5

What is the sum of the angles in any triangle?

• 270 degrees

• 360 degrees

• 90 degrees

• 180 degrees

Tags

CCSS.8.G.A.5

If one angle in an isosceles triangle is 40 degrees, what is the measure of each of the base angles?

• 90 degrees

• 80 degrees

• 70 degrees

• 60 degrees

Tags

CCSS.8.G.A.5

What is the measure of the third angle in an isosceles triangle if the other two angles are 70 degrees each?

• 40 degrees

• 70 degrees

• 60 degrees

• 80 degrees

Tags

CCSS.8.G.A.5

What is the measure of each angle in an equilateral triangle?

• 120 degrees

• 90 degrees

• 60 degrees

• 45 degrees

Tags

CCSS.8.G.A.5