A right angle is an angle with a measurement of 90 degrees . When two lines cross each other so that all the angles have the same size, the result is four right angles. The top of the letter T is at right angles to the vertical line. Walls of buildings are usually at right angles to the floor . Two things that are at right angles are called " perpendicular " or "orthogonal". This is expressed using the ⊥ {\displaystyle \bot } symbol (such as in ℓ 1 ⊥ ℓ 2 {\displaystyle \ell _{1}\,\bot \,\ell _{2}} ). [1] [2] [3]
Planes (flat surfaces) can also meet at right angles. In a building, a wall and a floor are said to be perpendicular to each other, and they have a right angle. It also can be called a square angle.