If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Special right triangles

3 videos
1 skill
We hate to pick favorites, but there really are certain right triangles that are more special than others. In this tutorial, we pick them out, show why they're special, and prove it! These include 30-60-90 and 45-45-90 triangles (the numbers refer to the measure of the angles in the triangle).

30-60-90 triangle side ratios proof

VIDEO 6:59 minutes
Proving the ratios between the sides of a 30-60-90 triangle

45-45-90 triangle side ratios

VIDEO 5:42 minutes
Showing the ratios of the sides of a 45-45-90 triangle are 1:1:sqrt(2)

30-60-90 triangle example problem

VIDEO 6:40 minutes
Using what we know about 30-60-90 triangles to solve what at first seems to be a challenging problem

Special right triangles