Similar triangles

Similar triangles are triangles that have the same angles, but different side lengths. The easiest way to think of this is to imagine a triangle being scaled up or scaled down.

• With similar triangles: angles are the same but side lengths are different
• To maintain the same internal angles, the ratio of the sides of similar triangles has to remain consistent.

If specific numbers aren’t given for a similar triangles problem, then it’s best to look at the shape of the triangle.

If the original triangle has relatively equilateral sides (is roughly symmetric) then a similar triangle will have to be similarly symmetrical. If the original triangle looks stretched to one side or very flat (long base and long sides), then the similar triangle has to be the same as well.