Right triangle
![Right triangle](/Images/godic/202502/06/Rtriangle.svg3814.png")
![Altitude of a right triangle](/Images/godic/202502/06/Teorema3814.png")
![Illustration of the Pythagorean Theorem](/Images/godic/202502/06/Illustration_to_Euclid's_proof_of_the_Pythagorean_theorem3814.png")
![Median of a right angle of a triangle](/Images/godic/202502/06/Thm_mediane.svg3814.png")
A right triangle (American English) or right-angled triangle (British English) is a triangle in which one angle is a right angle (that is, a 90-degree angle). The relation between the sides and angles of a right triangle is the basis for trigonometry.