Angles parallel lines

1. October 4, 2012
Angles
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2. Parallel lines

2. October 4, 2012
A straight line that crosses parallel lines is called the
transversal.
Angles at the same position are equal.
Explanation
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These are equal corresponding angles. They are in the
same position between the transversaland each parallel
line.

3. October 4, 2012
Alternate angles are on opposite sides of the transversal
and are equal.
You can think of a ‘Z’ shape to help you remember this.
Explanation
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4. October 4, 2012
The sum of interior angles is always 180º.
Interior angles are angles inside the parallel lines, on the
same side of the transversal.
Explanation
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5. October 4, 2012Example
If angle a is 120º,what is angle b?
a 120º
b120º
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6. October 4, 2012Example
If angle a is 60º,what is angle b?
a 60º
b60º
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7. October 4, 2012Example
If angle a is 72º,what is angle b?
72º
a 72º
b
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8. October 4, 2012Example
If angle a is 120º,what is angle b?
120º
a 120º
b
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9. October 4, 2012
125º
d
41º
r
Examples
What is angle d?
What is angle r?
55º
139º
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10. October 4, 2012
You may need to use your knowledge of both parallel
lines and triangles in a single question.
Angles are often labelled with single, lower case letters.
They may also be identified using upper case labels at
the ends of the lines.
You can also identify lines this way.
x
y
z
A
B C
Angle ACB
RLine AR
If angle ACB is 32º and angle y is 91º, what is angle x?
57º
32º
32º
91º
32 + 91 +?= 18057
Explanation
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