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A polygon is a 2-dimensional closed shape with straight sides. In this section we will revise the properties of polygons. Angle properties of triangles We already know that the angles in a triangle add up to 180°. Angles on a straight line also add up to 180°. In the diagram, we see that: a + b + c = 180° (angles in a triangle) and c + d = 180° (angles on a straight line). If we rearrange both equations (subtract c from both sides), we get: a + b = 180° - c and d = 180° - c. Therefore, a + b and d must be the same (they are both equal to 180° - c): a + b = d Now look again at the diagram. The exterior angle is equal to the sum of the two opposite interior angles. This is true for any triangle. Question Find each angle marked with a letter, giving reasons for your answer. Quadrilaterals The angles in a quadrilateral add up to 360º. There are other facts that you will need to know about special types of quadrilaterals. These are shown below: Square A square is a regular quadrilater

  Three‐dimensional objects are the solid shapes you see every day, like boxes, balls, coffee cups, and cans. Here are some helpful vocabulary terms for solids: Base : the bottom surface of a solid object. Edge : the intersection of two faces on a solid object. This is a line. Face : a flat side of a 3‐dimensional object. Prism : a solid object with two congruent and parallel faces. Pyramid : a solid object with a polygon for a base and triangles for sides. Say Hello to the 3-D Shapes Name Properties Picture Rectangular Prism A prism with rectangular bases. There are six faces. All faces meet at 90 degrees. Opposite faces are parallel. Cube A prism with six congruent faces. All faces meet at 90 degree angles. Opposite faces are parallel. It is a form of rectangular prism. Triangular Prism A prism with triangular bases. Only the bases are parallel. Octagonal Prism A prism with octagons for bases. Opposite faces are parallel. Triangular Pyramid, aka Tetrahedron A pyramid with a tria

Angles are measured in degrees, written °. The maximum angle is 360°. This is the angle all the way round a point. Half of this is the angle on a straight line, which is 180°. image: http://revisionworld.com/sites/revisionworld.com/files/imce/anglesums.GIF The video below explains how to calculate related angles, adjacent angles, interior angles and supplementary Lines AB and CD are parallel to one another (hence the » on the lines). a and d are known as vertically opposite angles. Vertically opposite angles are equal. (b and c, e and h, f and g are also vertically opposite). g and c are corresponding angles . Corresponding angles are equal. (h and d, f and b, e and a are also corresponding). d and e are alternate angles . Alternate angles are equal. (c and f are also alternate). Alternate angles form a 'Z' shape and are sometimes called 'Z angles'. a and b are adj