chord a line segment that goes through a circle, with its endpoints on the circle circumference the distance around a circle complementary angles two angles whose sum is 90° congruent identical in shape and size; the geometric symbol for congruent to is coordinate plane a grid divided into four quadrants by both a horizontal x -axis and a vertical y -axis coordinate points points located on a coordinate plane diagonal a line segment between two non-adjacent vertices of a polygon diameter a chord that passes through the center of a circle—the longest line you can draw in a circle. The term is used not only for this line segment, but also for its length. equiangular polygon a polygon with all angles of equal measure equidistant the same distance equilateral triangle a triangle with three equal sides and three equal angles exterior angle an angle on the outer sides of two lines cut by a transversal; or, an angle outside a triangle hypotenuse the longest leg of a right triangle. The hypotenuse is always opposite the right angle in a right triangle. interior angle an angle on the inner sides of two lines cut by a transversal isosceles triangle a triangle with two equal sides line a straight path that continues infinitely in two directions. The geometric notation for a line through points A and B is A B .
