Success Criteria

Aim• I can compare, classify and find unknown angles in polygons.

• I can find unknown angles in polygons.

• I can sort polygons using Venn and Carroll diagrams based on their properties.

Shape PerimeterCalculate the perimeter of this regular pentagon.

Shape PerimeterCalculate the perimeter of this isosceles trapezium.

3.4cm

6.1cm

Shape PerimeterCalculate the perimeter of this regular decagon.

1.3cm

Shape PerimeterCalculate the perimeter of this regular heptagon.

2.2cm

Shape PerimeterCalculate the perimeter of this kite.

3.5cm

2.8cm

Shape PerimeterCalculate the perimeter of this parallelogram.

3.8cm

2.6cm

Shape PerimeterCalculate the perimeter of this rhombus.

2.9cm

Shape PerimeterCalculate the perimeter of this regular octagon.

1.8cm

Polygon Angle PropertiesTo calculate a missing angle of a polygon we need to know the sum of

the interior angles of the polygon with the missing angle.

Use this formula to calculate the sum of the interior angles of a polygon:

( – 2) x 180number of sides

Polygon Interior AnglesUse the formula (number of sides – 2) × 180 to calculate the total

interior angles of the irregular polygons.

Polygon Missing Angles

113°

?°

If the sum of the interior angles of a pentagon is (5 - 2) x 180 = 540°, when four of the angles are given, we can calculate the missing angle.

Q: The pentagon ABCDE has: Angle A measuring 113°Angle B measuring 125°Angle C measuring 90°Angle D measuring 93°What is the measurement of angle E?

125°

93°

90°

A

B

C

D

E

Polygon Sortregular right angle

obtuse angle

Polygon Sortregular irregular

a ri

ght

angl

eno

rig

ht

angl

e