Presentation on theme: "Triangles and Quadrilaterals"— Presentation transcript:
1 Triangles and Quadrilaterals Level 4/5 BoosterLesson 8BTriangles and Quadrilaterals
2 rotational symmetry parallel opposite quadrilateral external angle Objectives:To identify and use the properties of triangles and quadrilaterals.Vocabulary:parallelrotational symmetryoppositequadrilateralexternal anglecongruent
3 Name the quadrilaterals and state their identifying properties: W/S 8.1B
4 ParallelogramOpposite sides equalOpposite sides parallelNo lines of symmetryRotational symmetry order 2
5 RectangleOpposite sides equal (and parallel)All angles 90ºTwo lines of symmetryRotational symmetry of order 2
6 RhombusAll sides equalOpposite sides parallelTwo lines of symmetryRotational symmetry of order twoIsosceles trapeziumOne pair of equal sidesOne pair of parallel sidesA line of symmetryNo rotational symmetry
7 SquareTrapeziumFour equal sidesOne pair of opposite sides parallelAll angles 90ºNo lines of symmetryFour lines of symmetryNo rotational symmetryRotational symmetry of order 4
8 You need W/S 8.2BUsing a 3 by 3 pinboard draw as many different triangles as you can find.ExampleThese two triangles are the same (congruent) – one is a translation of the other.These two triangles are the same (congruent) – one is a rotation of the other.
9 Here are the 8 different triangles that are possible.
12 Which of these triangles contain a right angle?
13 ˆ Conventional labelling: A B The marked angle is angle ADC or angle CDA.Sometimes written as <ADCor ADCDˆCHow would you describe the angle indicated in the same way?ABCDEstimate the size of angle BAD.ºWhat type of angle is angle ADC?Obtuse
14 ABCAB has been extended to point D.Angle CBD (marked) is an external angle of the triangle.DFollow these instructions:Draw a triangle and label the vertices A, B and C.Extend line BC to the point D and label point D.What do you know about the angles ACD and ACB?Angles ACD and ACB are on a straight line and therefore have a sum of 180º.
15 You have two congruent right-angled triangles You have two congruent right-angled triangles. What different quadrilaterals can you make by putting sides of equal length together?Example:parallelogramUsing two congruent right-angled triangles what other shapes can you make?
16 Here are the quadrilaterals you can find. Other shapes you can produce are:
17 rotational symmetry parallel opposite quadrilateral external angle Objectives:To identify and use the properties of triangles and quadrilaterals.Vocabulary:parallelrotational symmetryoppositequadrilateralexternal anglecongruent