Triangles and Their Properties

Front

Triangle

Back

A polygon with three sides and three angles.

Front

Vertex (of a Triangle)

Back

A point where two sides of a triangle meet (a corner). A triangle has three vertices.

Front

Acute Triangle

Back

A triangle in which all three angles are acute (less than 90°).

Front

Right Triangle

Back

A triangle that has exactly one right angle (equal to 90°).

Front

Obtuse Triangle

Back

A triangle that has exactly one obtuse angle (greater than 90° but less than 180°).

Front

Equiangular Triangle

Back

A triangle in which all three angles are congruent (equal in measure). Each angle in an equiangular triangle measures 60°.

Front

Equilateral Triangle

Back

A triangle in which all three sides are congruent (equal in length). An equilateral triangle is also equiangular.

Front

Isosceles Triangle

Back

A triangle that has at least two sides congruent (equal in length). The angles opposite these sides are also congruent.

Front

Scalene Triangle

Back

A triangle in which no two sides are congruent (all three sides have different lengths), and no two angles are congruent.

Front

Hypotenuse

Back

The side opposite the right angle in a right triangle. It is always the longest side.