There are three types of triangles:
Equilateral triangle – all sides and angles are equal
Isosceles triangle – two sides and angles are equal
Scalene triangle – none of the sides or angles are equal
Triangles can also be named according to their angles:
Right angled triangle – contains a right angle
Acute angled triangle – contains acute angles
Obtuse angled triangle – contains an obtuse angles
Angles in a triangle
All angles in a triangle add up to 180°.
Any exterior angle in a triangle is equal to the sum of the two opposite interior angles.