Y9 Angles

1
Y9 Angles

• Level 6 and 7
• 10th April 03

2
D
Draw an isosceles triangle ABC.
B
Mark the equal angles and sides.
Mark and shade the angle ABC
Extend line AB to point D
C
Mark the exterior angle of the triangle
A
D
Alternatively,
B
C
A
3
Follow these instructions
Draw a pair of parallel lines with an
intersecting transversal.
Label the parallel lines
Label a pair of corresponding angles with the
letter c
c
c
c
c
c
c
c
c
c
c
c
c
4
Follow these instructions
Draw a pair of parallel lines with an
intersecting transversal.
Label the parallel lines
Label a pair of corresponding angles with the
letter c
Label a pair of alternate angles with the letter a
a
a
a
a
a
a
a
a
a
a
a
a
5
Follow these instructions
Draw a pair of parallel lines with an
intersecting transversal.
Label the parallel lines
Label a pair of corresponding angles with the
letter c
Label a pair of alternate angles with the letter a
Label a pair of vertically opposite angles with
the letter v
v
v
v
v
v
v
6
Isosceles trapezium M8.1

• ABCD is an isosceles trapezium with AB parallel
  to DC.
• P is the midpoint of AB, and AP CD, AD DP.
• ?DAP 75.
• Calculate the sizes of the other angles.

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Isosceles trapezium
AB parallel to CD
75º
P is the midpoint of AB
AP DC and AD DP
DAP 75º
What is the size of angle APD and why?
What is the size of angle ADP and why?
What is the size of angle PBC and why?
What can you say about triangles APD and BPC?
Which angles does this help you to find?
The base angles of the isosceles trapezium ( BAD
and ABD) are equal, how does this help you find
angles ADC and ACD?
8
Star
M8.2

• The shape left has three identical white tiles
  and three identical grey tiles.
• The sides of each tile are the same
  length.Opposite sides of each tile are parallel.
• One of the angles is 70. (a) Calculate the size
  of angle k.Give a reason for your answer.
• (b) Calculate the size of angle m.Give a reason
  for your answer.

9
Grey tiles are congruent White tiles are
congruent.
All sides are the same length and opposite sides
are parallel
What is the name for a quadrilateral with four
sides the same length and opposite sides parallel?
What other properties does this shape have?
The white tile has an angle of 70º what is the
size of its other angles?
The angles at the centre of the compound shape
have a total of?
There are 3 angles which measure 70º. What is
the angle in each of the grey shapes at the
centre?
70º