Types and Properties of Triangles

Equilateral Triangles

Triangles with all three sides equal in length and all three angles equal in magnitude, are called equilateral triangles. Since the angles in a triangle sum to 180° and the size of each angle is the same in an equilateral triangle, the angles are all 60°.

Isosceles Triangles

Isosceles triangles are triangles with two sides equal in length and two angles equal in magnitude.

Scalene Triangles

A scalene triangle is one which has no sides equal in length and no angles equal in magnitude.

Right-Angled Triangles

Right-angled triangles are triangles with one of their angles equal to 90° (i.e. a right angle).

Obtuse-Angled Triangles

Obtuse-angled triangles are triangles with one of their angles greater than 90° but less than 180° (i.e. an obtuse angle).

Acute-Angled Triangles

Acute-angled triangles are triangles in which all the angles are acute. That is, all angles are greater than 0° but less than 90°.

Congruent Triangles

Congruent triangles are triangles which have the same area, angles and side lengths.

Similar Triangles

Similar Triangles are triangles which have the same sized angles.