Rightangled

Rightangled is an adjective used in geometry to describe figures or angles that include a right angle, meaning an angle of 90 degrees. The term is most common in British English as right-angled; in American English, the phrase is understood but less frequently used. In geometry, a right-angled figure has sides or angles that meet perpendicularly.

In a right-angled triangle, one interior angle measures 90 degrees. The side opposite that angle is the hypotenuse, the longest side. The other two sides are called the legs. The Pythagorean theorem applies: a^2 + b^2 = c^2. Trigonometry relates the acute angles to ratios of the sides via sine, cosine, and tangent: sin(angle) = opposite/hypotenuse, with corresponding relations for the other functions.

Beyond triangles, right-angled describes polygons with a 90-degree angle. A rectangle is a polygon whose interior angles are all right angles. A right-angled trapezoid is a trapezoid with two right angles. In coordinate geometry, a right-angled orientation refers to axes that meet at 90 degrees.

The term emphasizes perpendicularity and is closely related to concepts such as perpendicular and orthogonal in Euclidean geometry.