3. Angle calculations a 72 0 21 0 Angles in a half turn = 180 0 Angles in a full turn = 360 0 162 0 b 135 0 Opposite angles are equal 153 0 c d e Angles in a triangle = 180 0 j12 0 35 0 F angles are equal 57 0 hi Z angles are equal 42 0 fg 98 0 73 0 k l Angles in a quadrilateral = 360 0 Angles in an isosceles triangle m 8080 Use the rules to work out all angles

4. Angles and polygons e e e c c c c c c ie Interior = 180 - e angles Angles at = 360 the centre No. of sides Exterior = 360 angles No. of sides There are 3 types of angles in regular polygons Calculate the value of c, e and i in regular polygons with 8, 9, 10 and 12 sides Answers: 8 sides = 45 0, 45 0, 135 0 9 sides = 40 0, 40 0, 140 0 10 sides = 36 0, 36 0, 144 0 12 sides = 30 0, 30 0, 150 0 To calculate the total interior angles of an irregular polygon divide it up into triangles from 1 corner. Then no. of x 180 Total i = 5 x 180 = 900 0