No. 1 A 90 2 = 45 180 - 45 45 = 135 (180 - 45 ) 2 = 67.5 - PowerPoint PPT Presentation

No. 1

A 90  ÷ 2 = 45  180  - 45  45  = 135  (180  - 45  ) ÷ 2 = 67.5  180  - 90  - 45  B = 45  90  90  E C F 90  67.5  - 22.5  180  - 90  - 67.5  = 45  = 22.5  D 67.5 

Can you name this shape? Isosceles triangle

 What can you tell me about the isosceles triangle?  Look at the sides and angles.  What about lines of symmetry?  Will it tessellate?  What shapes can you make with 1, 2, 3, or more of these shapes?

In an isosceles triangle, there are two equal sides. In an isosceles triangle, there are two equal angles.

What shapes can you make with 1, 2, 3, or more of these shapes? An isosceles triangle can tessellate. Isosceles triangle

How many lines of symmetry are there in an isosceles triangle? 1

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In the figure, not drawn to scale, AB=AC. Find  ABC. A Sum of angles of a triangle is 180 ° .  ABC=  ACB 80°     180 80 100   2 2   50 C B

No. 2

Can you name this shape? Right-angled triangle

Right-angled triangle  What can you tell me about this right-angled triangle?  Look at the sides and angles.  What about lines of symmetry?  Will it tessellate?  What shapes can you make with 1, 2, 3, or more of these shapes?

How many lines of symmetry are there in this triangle? 1

What shapes can you make with 1, 2, 3, or more of these shapes? A right- angled triangle can tessellate.

EFG is a right-angled triangle. EGI is a straight line and GHI is an isosceles triangle. Find  FGH. H    HGI HIG   52  180 - 52    64 2 F 64  96  64  I 20  70   FGE=180  - 90  - 70  G E = 20   FGH=180  - 20  - 64  = 96 

No. 3

Can you name this shape? Equilateral triangle

What is special about an equilateral triangle?  What can you tell me about an equilateral triangle?  Look at the sides and angles.  What about lines of symmetry?  Will it tessellate?  What shapes can you make with 1, 2, 3, or more of these shapes?

How many lines of symmetry are there in an equilateral triangle ? 3

In an equilateral triangle, there are three equal sides.

In an equilateral triangle, the three a angles are equal. b c  a +  b +  c = 180 °  a =  b =  c =180 °÷ °÷ 3 = 60 °

ABCD is a square. QM=QP=QN. MN is perpendicular to PQ. Find  MPN Since, given that A P B QM=QP=QN= MN 150  Therefore triangle MNQ is N M an equilateral triangle .  MQN=180  3=60   MQP=60  2=30  Triangle MQP is an isosceles triangle. 30   180 30     MPQ 75 2 D C Q  MPN=75  2=150 

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