Geometry · Similarity & Right Triangles
45-45-90 Triangle
HSG-SRT.C.8
Definition
An isosceles right triangle whose hypotenuse equals a leg × √2.
Examples
- If each leg is 1, the hypotenuse is √2, giving a side ratio of 1 : 1 : √2.
- If each leg is 5, the hypotenuse is 5√2.
Key rule
In a 45-45-90 triangle, the two legs are always equal.
Memory hook
Equal legs, hypotenuse is a leg × √2.