1. Angle Bisectors – Worksheet A
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4. 1 Angle Bisectors 1 2 3 4 5 1 2 3 4 5 Only using a compass and ruler….
1) Create a line starting at A, perpendicular to BC.
(To start, you need to mark two places that are equidistant from A.
Then, you can construct a perpendicular bisector.)
The line has been angled at A.
2) Repeat the same process to make a perpendicular bisector but join it to A.
(Start by finding two places equidistant from A on both lines.) B C B A C A
Is the perpendicular bisector
actually perpendicular now?
3) Follow the same process. Which number does your bisector hit?
4) Angle BAC is 100°
Can you make an angle of 50° without using a protractor?
Which number does the line bisector hit? 1 2 3 4 5 B 1 2 3 4 B 5 A C
100° C A
What can we say about this line and BAC?

5. Perpendicular Bisector
90°
Cut in half.

6. Angle Bisector B A C

7. 2 1 Answers 1 Angle Bisectors 1 2 3 4 5 1 2 3 4 5
Only using a compass and ruler…. 1
1) Create a line starting at A, perpendicular to BC.
(To start, you need to mark two places that are equidistant from A.
Then, you can construct a perpendicular bisector.)
The line has been angled at A.
2) Repeat the same process to make a perpendicular bisector but join it to A.
(Start by finding two places equidistant from A on both lines.) B C C B A
Answers A
Is the perpendicular bisector
actually perpendicular now?
3) Follow the same process. Which number does your bisector hit? 2
4) Angle BAC is 100°
Can you make an angle of 50° without using a protractor?
Which number does the line bisector hit? 1 1 2 3 4 5 B 1 2 3 4 B 5 A C
100° C A
What can we say about this line and BAC?

8. 2 3 1 2 Answers 2 Angle Bisectors 1 2 3 1 4 2 3 2 1 3 1 3 2 4
Only using a compass and ruler…. 2 2 3
1) Bisect the angle BAC. Which number does it hit?
2) Bisect the angle BAC. Which number does it hit? B 1 2 B 3 1 4 2 3 A A C C
3) Create a 45 ° angle at A. Which number does it hit?
(How can we make a 90° angle first?)
4) Which number is equidistant from all sides of this triangle?
First, construct a line that is equidistant from AB and AC. 1 2 1 3 B 2 1 3 2 4 B C
Answers A A C

9. 1 Angle Bisectors 1 2 3 4 5 1 2 3 4 5 Only using a compass and ruler….
1) Create a line starting at A, perpendicular to BC.
(To start, you need to mark two places that are equidistant from A.
Then, you can construct a perpendicular bisector.)
The line has been angled at A.
2) Repeat the same process to make a perpendicular bisector but join it to A.
(Start by finding two places equidistant from A on both lines.) B C B A C A
Is the perpendicular bisector
actually perpendicular now?
3) Follow the same process. Which number does your bisector hit?
4) Angle BAC is 100°
Can you make an angle of 50° without using a protractor?
Which number does the line bisector hit? 1 2 3 4 5 B 1 2 3 4 B 5 A C
100° C A
What can we say about this line and BAC?

11. Angle Bisectors
Only using a compass and ruler…. 2
1) Bisect the angle BAC. Which number does it hit?
2) Bisect the angle BAC. Which number does it hit? B 1 2 B 3 1 4 2 3 A A C C
3) Create a 45 ° angle at A. Which number does it hit?
(How can we make a 90° angle first?)
4) Which number is equidistant from all sides of this triangle?
First, construct a line that is equidistant from AB and AC. 2 1 3 B 1 3 2 4 B C A A C

14. tom@goteachmaths.co.uk Questions? Comments? Suggestions?
…or have you found a mistake!?
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