right angles

In geometry and trigonometry, a right angle is an angle of 90 degrees, corresponding to a quarter turn (that is, a quarter of a full circle). It can be defined as the angle such that twice that angle amounts to a half turn, or 180° .Lines that are at a right angle to each other are perpendicular, an important geometrical property. The presence of a right angle in a triangle is the defining factor for right triangles.A right angle may be expressed in different units:90°π/2 radians100 grad (also called grade, gradian, or gon)8 points (of a 32-point compass rose)6 hours (astronomical hour angle)∞% grade on the tangent scale100% grade on the sine scale.
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