Angle calculations

a720 210

Angles in a half turn = 1800

Angles in a full turn = 3600

1620

b1350

Opposite angles are equal

1530

cde

Angles in a triangle = 1800

j120

350

“F” angles are equal

570

h i

“Z” angles are equal

420

f g

980

730k

l

Angles in a quadrilateral = 3600

Angles in an isosceles triangle

m80

Use the rules to

work out all angles

Angles and polygons

e

e

e

c c

cccc 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 = 450, 450, 1350

9 sides = 400, 400, 1400

10 sides = 360, 360, 1440

12 sides = 300, 300, 1500

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 = 9000