QUADRATURE

in mathematics, process of determining the area of a plane geometric figure by dividing it into a collection of shapes of known area (usually rectangles) and then finding the sum of these areas. When this process is performed with solid figures to find volume, the process is called cubature. A similar process called rectification is used in determining the length of a curve. The curve is divided into a sequence of straight line segments of known length. Because the definite integral of a function determines the area under its curve, integration is still sometimes referred to as quadrature. in astronomy, that aspect of a heavenly body in which its direction as seen from the Earth makes a right angle with the direction of the Sun. The Moon at First or Last Quarter is said to be at east or west quadrature, respectively. A superior planet (outside the Earth's orbit) is at west quadrature when its position is 90 west of the Sun. It rises around midnight, reaches the meridian (a great circle on the celestial sphere, passing through the north and south poles and the zenith) near sunrise and sets near noon. At east quadrature the planet is near the meridian at sunset and sets near midnight. At both quadratures the planet is at gibbous phase (more than half but not all of the disk illuminated), but only Mars shows up conspicuously gibbous.