- In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or 𝜋/2 radians corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin angulus rectus; here rectus means “upright”, referring to the vertical perpendicular to a horizontal base line.
- Right triangle (Wikipedia)
A right triangle or right-angled triangle, sometimes called an orthogonal triangle or rectangular triangle, is a triangle in which two sides are perpendicular forming a right angle (1⁄4 turn or 90 degrees).
