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Congruent and similar triangles

Congruent and similar triangles. You are going to draw a triangle onto card or paper You will need a ruler and compasses to construct it. Using a ruler and compasses only, this is how to construct a triangle of sides 8 cm, 7 cm & 4 cm. Draw a line of 8 cm.

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Congruent and similar triangles

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  1. Congruent and similar triangles

  2. You are going to draw a triangle onto card or paper You will need a ruler and compasses to construct it

  3. Using a ruler and compasses only, this is how to construct a triangle of sides 8 cm, 7 cm & 4 cm Draw a line of 8 cm Put the point of compasses here & draw an arcs of radius 7 cm Put the point here & draw an arc of radius 4 cm 7 cm 4 cm 8 cm On card, construct 2 triangles with sides 8 cm, 7cm & 4 cm Cut them out

  4. Your two triangles are the same shape and size They are congruent

  5. This is how to construct an equilateral triangle using a ruler and compasses Put the point of compasses here & draw two arcs of equal radius Keep the radius the same, put point here & draw another arc On card, construct 2 equilateral triangles of different sizes. Cut them out.

  6. Your two triangles are the same SHAPE They are similar They are different SIZES

  7. On card, draw 2 different triangles with base angles 75º and 55º Use a ruler and protractor 55º Cut them out 75º Measure the third angles (They should both be 50º)

  8. These two triangle have the same shape but are different sizes They are similar triangles They have the same angles

  9. Which triangle is not similar to the others? Answer

  10. These two triangles are both equilateral. Are they similar? Answer YES

  11. Problems involving triangles can be solved by scale drawing

  12. Scale drawings are similar to the real thing

  13. North The map shows the journey of a ship. Island The ship leaves the Port, sails 30 miles North, then 20 miles East. MAP N Make a scale drawing & produce a similar diagram. I How far is the Island from the port ? ? Port DRAWING P

  14. End

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