Isosceles Triangle

My Definition

Key Characteristics

The following are true of an isosceles triangle:

  • It is a triangle with at least two sides of equal length.

  • It has a vertex angle created by two equal sides of the isosceles triangle.

  • The side opposite the vertex angle is the base.

  • The measures of the base angles are equal.

  • An equilateral triangle is an example of an isosceles triangle.


As you use the sliders to change the length of the base and the height of the isosceles triangle, what do you notice about the lengths of the other two sides and the measures of the base angle?

Isosceles Triangle Activity


TEKS: 6(8)(A), 7(11)(C)