Triangles are polygons with three sides.

An acute − angled triangle contains no angles greater than 90°.

e.g. A , B and C are all acute angles.

A right − angled triangle contains an angle of 90°.

e.g. A = 90°

e.g. sides: a = b

angles: A = B

An equilateral triangle is one in which all three sides are of equal length and each interior angle is 60°.

An equilateral triangle has three axes of symmetry.

e.g. sides: a = b = c

angles: A = B = C