Classifying Triangles

Classifying by Angle

• Acute triangles have three acute angles.

• Obtuse triangles have one obtuse angle.

• Right triangles have one right angle.

Classifying by Sides

• Equilateral triangles have three congruent sides.

• Isosceles triangles have two congruent sides.

• Scalene triangles have zero congruent sides.

Finding Missing Angles• The three angles of a triangle always

add to 180°.

• Use a variable to stand for the missing angle and set an equation equal to 180.

x + 49 + 47 = 180x + 96 = 180 – 96 = -96

x = 84