Triangles: A Reference Sheet
Triangles have three sides and three angles.
The sum of the three angles of every triangle is 180 degrees.
Classifying Triangles Using Their Angles
Acute Triangle
Obtuse Triangle
Right Triangle
All angles are acute.
One right angle
Other angles are acute.
Equilateral Triangle
One obtuse angle
Other angles are acute.
Scalene Triangle
Isosceles Triangle
All 3 side lengths measure the same.
Two sides measure the same.
None of the sides measure the same.
All 3 angles have the same measure
also.
As a result, the two base angles
measure the same.
As a result, none of the angles measure
the same.
Special Names for Sides
The sides of the isosceles and the right triangle have special names.
Examine the diagrams for vocabulary words for each of these triangles.
Isosceles Triangle
leg
leg
base
Right Triangle
hypotenuse
leg
leg