Geometry 904 Ninth grade students learn points and lines, line segments, rays, planes, and lines and points in planes. They study definitions of angles and degrees and measuring the size of angles. They learn to classify angles by size and relation and how to bisect an angle. Students study parallelograms, properties of a trapezoid, ratio and proportions, and the Pythagorean Theorem. Ninth grade students know derive and solve problems involving the perimeter, circumference, area, volume, lateral area, and surface area of common geometric figures. Students know the definitions of basic trigonometric functions defined by the angles of a right triangle. They also know and are able to use elementary relationships between functions.