Types and Properties of 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 are triangles with two sides equal in length and two angles equal in magnitude.
A scalene triangle is one which has no sides equal in length and no angles equal in magnitude.
Right-angled triangles are triangles with one of their angles equal to 90° (i.e. a right angle).
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 are triangles in which all the angles are acute. That is, all angles are greater than 0° but less than 90°.
Congruent triangles are triangles which have the same area, angles and side lengths.
Similar Triangles are triangles which have the same sized angles.