455-467

2D shapes

· Have length and width

· Grouped by side attribute

o Straight lines – polygon

o Curves

o Straight lines and curves

· Also:

o Closed – all lines meet

o Not closed – not all lines meet

o Simple – lines don’t cross

o Not simple – lines do cross

· Also:

o Concave – interior angle greater than 180

o Convex – interior angles 180 or less

Polygons

Poly = many Gons= angles

· Regular - angles are the same

· Irregular – angles are different

· Difficulties

o Not recognizing different sizes as being same shape

o Different examples of same shape (eg. regular and irregular quadrilaterals)

o Different orientations are still same shape

o Only recognizing stereotype of the shape

Triangles

3 angles – total 180

· Scalene – no equal sides or angles

· Isosceles – 2 equal sides and angles

· Equilateral – 3 equal sides and angles, 60 each

· Acute angle – less than 90

· Obtuse angle – more than 90

· Right angle – exactly 90

· Difficulties

o Right angle is seen as half a triangle

o Right angle with a left orientation is a left angles

o Chevron or arrow is confused with triangle

o Orientation issues

Quadrilaterals

4 sides

· Sum of angles is 360

· Closed shape with 4 sides

· Oblong/rectangle

o All right angles

· Square

o Right angles with equal length sides

· Rhombus

o 2 obtuse angles

o 2 right angles

o Equal sides

o Diagonals at right angles (they add up to 180)

· Kite

o Angles less than 180

o Adjacent sides equal

o Diagonals at right angles (they add up to 180)

· Arrowhead

o Adjacent sides equal

o One angle greater than 180

· Parallelogram

o Opposite sides equal

o 2 sets parallel lines

· Difficulties

o Sterotyped views

o Diamond is not a math term, it’s a rhombus or turned square

o Not understanding orientation doesn’t affect (may think rectangle has parallel line to bottom of page)

Geoboards

· Equally spaced rows of nails

· Use rubber bands

· Can quickly make and experiment with 2d shapes

· Use dot paper to record

Angles

· The amount of turn

· Full turn is 360

· Straight line is 180

· When line intersects straight line, deduct known angle from 180 to find unknown

· Opposite angles are equal

· Triangle = 180

· Quadrilateral = 360

· Can work out other shapes by seeing how many triangles fit in it (eg. 3 triangles fit in pentagon so 180 x 3 = 540 degrees)

468-469

Circles, ellipses, ovals

· Curved line

· Everyday objects like coin, wheel, football field, jar lids

· Circumference – length around circle

· Radius – length from center to outside

· Centre – middle point

· Diameter – length from one side to other

· Ellipse – 2 fixed points with major and minor axis of symmetry

· Oval – one axis of symmetry

· Difficulties

o Football ‘oval’ is an ellipse

o Circles are described as round rather than circular

429-431

Angles

1. Identify attribute angle

o Use rotagrams, angle arms and wheels – these are dynamic and show turn

o Angle as a corner

o Angle as a shape

o Angle as a measure of turn

2. Comparing and ordering angles

o Direct comparison by layering

o Use rotagram to show turn (bigger or smaller)

3. Measuring angles non-standard

o Fold paper to show

o Half turn

o Quarter turn

o Estimate the amount of turn

4. Measuring angles using standard

o Dividing 360 to get:

o 180 half

o 90 quarter

o Then use full circle protractor (connect to rotagram)

Difficulties

· Longer lines is a bigger angle

· Different orientations

· Left or wrong angle

· Half scale protractor difficult as not sure which direction to follow

417-418

· Use peg, rope and chalk to create a circle

· Highlights constant distance of the radius

· Use paper circle in half to show diameter

· Circumference is 3 times longer than diameter

· 3.14 = d x c

· use pi and symbol last after relationship established

	Created by Ashleigh Collins over 10 years ago

2 Math Year 2 (Geometry) Note on Geometry, created by Ashleigh Collins on 28/04/2016.