The triangles family consists of four basic types of triangle: equilateral, where all the angles are 60 degrees and the sides are the same length; isosceles, where two angles are the same and two sides have the same length; right-angled, where one angle is 90 degrees; scalene, where no angles or sides are the same. An isosceles triangle can also right-angled, in which case the angles are 45, 45 and 90 degrees and the sides that included the right angle are the same length. Similar triangles have identical angles to one another but differ in size. Congruent triangles also have identical angles, but they also have matching sides of the same length, and can be mirror images of one another.