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Properties of geometric figures – beginner

This lesson comprises four (4) master classes focusing on:

  • Angle notations and conventions
  • Properties of triangles, quadrilaterals and polygons
  • Line symmetry and rotational symmetry
  • Reflection, translation and rotation
  • Congruent figures
  • Similar figures

Content:

MA4-GEO-C-01


Classify triangles according to their side and angle properties

  • Label triangles using appropriate text and symbols
  • Classify and describe types of triangles based on their properties, including acute-angled, right-angled, obtuse-angled, equilateral, isosceles and scalene triangles

Classify quadrilaterals and describe their properties

  • Identify quadrilaterals using naming conventions
  • Distinguish between convex and non-convex quadrilaterals
  • Verify and describe the properties of the special quadrilaterals which include parallelograms, rectangles, rhombuses, squares, trapeziums and kites
  • Identify and label the properties of the special quadrilaterals using appropriate conventions
  • Classify quadrilaterals based on their properties
  • Justify why some quadrilaterals may be classified as more than one type of quadrilateral

Apply the properties of triangles and quadrilaterals

  • Prove that the interior angle sum of a triangle is 180° with or without digital tools
  • Prove that any exterior angle of a triangle equals the sum of the 2 interior opposite angles
  • Apply the angle sum of a triangle to prove that the angle sum of a quadrilateral is 360°
  • Apply the properties of triangles and quadrilaterals to determine unknown sides and angles to solve problems, giving reasons

 

MA5-GEO-C-01


Identify and describe the properties of similar figures

  • Describe similar figures as having the same shape but not necessarily the same size
  • Verify and explain that in similar polygons, the corresponding angles are equal and the corresponding side lengths are in the same proportion
  • Name the vertices in matching order when using the similar symbol  \( (\sim) \) in a similarity statement
  • Match the corresponding sides and angles of similar polygons

Solve problems using ratio and scale factors in similar figures

  • Apply an appropriate scale to enlarge or reduce a diagram
  • Determine the scale factor for pairs of similar polygons and circles
  • Apply knowledge of scale factor to find unknown sides in similar polygons
  • Solve problems involving unknown lengths and scale factors of similar figures and related practical problems
  • Solve problems involving scale drawings, with or without digital tools

 

MA5-GEO-P-01


Identify and explain congruence

  • Identify figures as congruent figures if translations, reflections and rotations can move one figure exactly on top of another
  • Match the sides and angles of 2 congruent polygons
  • Indicate 2 polygons are congruent using the symbol \( (\equiv) \) and name the vertices in matching order
  • Determine that having equal radii is the condition for 2 circles to be congruent

Develop and use the conditions for congruent triangles

  • Establish the 4 congruence tests for triangles (SSS, SAS, AAS and RHS)
  • Use the congruence tests to identify a pair of congruent triangles from a selection of 2 or more triangles

Develop and apply the minimum conditions for triangles to be similar

  • Examine the minimum conditions needed and establish the 4 tests for 2 triangles to be similar
  • Apply the minimum conditions needed and determine whether 2 triangles are similar using an appropriate test

Establish and apply properties of similar shapes and solids

  • Establish for 2 similar figures with similarity ratio \( a:b \) that their areas are in the ratio \( a^2:b^2 \) and their volumes are in the ratio \( a^3:b^3 \)
  • Solve problems involving areas and volumes of similar shapes and solids

Apply logical reasoning to numerical problems involving plane shapes

  • Apply geometrical facts, properties and relationships to find the sizes of unknown sides and angles of plane shapes in diagrams, providing appropriate reasons
  • Define the exterior angle of a convex polygon
  • Establish the sum of the exterior angles of any convex polygon is \( 360^\circ \) and verify this result
  • Apply the result for the sum of the interior angles of a triangle to find, by dissection, the sum of the interior angles of a polygon with more than 3 sides
  • Apply the results for the interior and exterior angles of polygons to solve problems involving polygons