A 30-60-90 triangle can be formed by cutting an equilateral triangle in half. This is one of two special types of right triangles (the other is a 45-45-90 triangle, which is half of a square).

What do you know about the sides of equilateral triangle? All 3 sides of an equilateral triangle have the same length.

Let's say you have an equilateral triangle and all three sides are 10 units long. If you cut the equilateral triangle in half, it forms a 30-60-90 triangle. If the hypotenuse of the triangle is 10, what is the length of the shorter leg of the 30-60-90 triangle?

Do you know how long the missing side will be? The bottom side has been cut in half to form the 30-60-90 triangle, so it must be half of 10: 5 units long.