Properties of Isosceles Triangles

The video tutorial covers the properties and theorems of isosceles and equilateral triangles, including their base angles and congruency. It explains how to solve problems using these properties and introduces corollaries related to equilateral triangles. The tutorial also includes practice problems and a coordinate proof demonstrating that a triangle formed by the midpoints of an isosceles triangle is also isosceles.

What is the definition of the base in an isosceles triangle?

• The side opposite the vertex angle

• The side equal to the legs

• The angle between the legs

• The longest side of the triangle

In an isosceles triangle, what are the angles along the base called?

• Vertex angles

• Supplementary angles

• Base angles

• Leg angles

What does the theorem about isosceles triangles state regarding base angles?

• Base angles are complementary

• Base angles are always different

• Base angles are congruent

• Base angles are supplementary

If the base angles of a triangle are congruent, what can be inferred about the triangle?

• It is a right triangle

• It is an equilateral triangle

• It is a scalene triangle

• It is an isosceles triangle

How do you find the measure of an angle in an isosceles triangle if you know the other two angles?

• Multiply the known angles by 2

• Add the known angles and divide by 2

• Subtract the known angles from 360°

• Subtract the sum of the known angles from 180°

What is a corollary in the context of geometry?

• A theorem that is always false

• A minor theorem derived from a major theorem

• A statement that contradicts a theorem

• A theorem that applies only to circles

What is true about the angles in an equilateral triangle?

• They are all 90°

• They are all different

• They are all 45°

• They are all 60°

If a triangle is equiangular, what can be said about its sides?

• The sides are in a 2:1 ratio

• The sides form a right triangle

• The sides are all equal in length

• The sides are all different lengths

What is the result of dividing the sum of angles in a triangle by the number of angles?

• 45°

• 60°

• 30°

• 90°

What is the significance of the midpoints in the proof involving isosceles triangles?

• They form a right triangle

• They form an equilateral triangle

• They form another isosceles triangle

• They form a scalene triangle