The Angle A of Quadrilateral is the space between two intersecting lines( side a and side d) or surfaces at or close to the point where they meet. And is denoted by ∠A. Angle A of Quadrilateral is usually measured using the Degree for Angle. Note that the value of Angle A of Quadrilateral is always positive. Typically, the value of Angle A of Quadrilateral lies in the range from 0 to 180.