April 13, 2023

Angles

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2. Parallel lines

April 13, 2023

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 transversal and each parallelline.

April 13, 2023

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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April 13, 2023

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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April 13, 2023Example

If angle a is 120º,what is angle b?

a 120º

b120º

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April 13, 2023Example

If angle a is 60º,what is angle b?

a 60º

b60º

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April 13, 2023Example

If angle a is 72º,what is angle b?

72º

a 72º

b

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April 13, 2023Example

If angle a is 120º,what is angle b?

120º

a 120º

b

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April 13, 2023

125ºd

41ºr

Examples

What is angle d?

What is angle r?

55º

139º

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April 13, 2023

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.

xyz

A

B C

Angle ACB

R Line 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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