1. A locus (pl. loci) is a Set of Points satisfying certain criteria.
For
A.S 1.4 Use Geometric Techniques to Produce a Pattern or Object.
Internal, 2 Credits
Section
Single Point
Single Line
Two Fixed Points
Two Fixed Lines

2. Constructing the set of points Equidistant from a point A: eg
Constructing the set of points Equidistant from a point A: eg. construct the set of points 3cm from Point A. (click once to start)
1. Construct the circle, centre A with radius 3cm.
This is the set of points equal to 3cm from point A.
 A
3 cm
Locus of points related to a Single Point
Equidist1
Within(1pt)
Less than(1pt)
Greater than(1pt)

3. Constructing the set of points within a certain distance from a point: eg. construct the set of points within 3cm from Point A. (click once to start)
1. First construct the set of points equal to 3cm from point A ie the circle shown.
2. Shade the area inside the circle
The shaded area is the set of points less than or equal to 3cm from point A
 A
3 cm
Locus of points related to a Single Point
Equidist1
Within(1pt)
Less than(1pt)
Greater than(1pt)

4. Constructing the set of points less than a certain distance from a point:
Use a dashed line on the circumference to show that the circumference itself is not included.
The shaded area is the set of points less than 3cm from point A
 A
3 cm
Locus of points related to a Single Point
Equidist1
Within(1pt)
Less than(1pt)
Greater than(1pt)

5. Constructing the set of points greater than a certain distance from a point:
(Use a dashed line on the circumference to show that the circumference itself is not included.)
Shade outside the circle.
The shaded area is the set of points greater than 3cm from point A
 A
3 cm
Locus of points related to a Single Point
Equidist1
Within(1pt)
Less than(1pt)
Greater than(1pt)

6. Locus of points related to a Fixed Line
The Locus of Points equidistant from a fixed Line (click once to start)
Eg. The locus of points 3 cm from line AB.
There are two lines 3cm from line AB B
3 cm A
Locus of points related to a Fixed Line
fixed Line
fixed Line Segment

7. Locus of points related to a Fixed Line
The Locus of Points equidistant from a fixed Line Segment (click once to start)
Eg. The locus of points 3 cm from line segment AB.
There are two semicircles as well as two lines B
3 cm A
Locus of points related to a Fixed Line
fixed Line
fixed Line Segment

8. Locus of points related to Two Fixed Points
The set of Points equidistant from two fixed points A and B (click once to start)
Bisect the line joining A and B
 B
 A
Locus of points related to Two Fixed Points
Equidistant to2 pts
Closer to pt A than B

9. The set of Points closer to point A than Point B (click once to start)
1. Bisect the line joining A and B
2. Shade the side closer to A than B.
 B
3. Make the line dashed to show that it is not included in this set of points.
 A
Locus of points related to Two Fixed Points
Equidistant to2 pts
Closer to pt A than B

10. Locus of Points Equidistant to two Fixed Lines. (click once to start)
1. Bisect angle AXC and extend
2. Bisect angle AXD and extend C
Each point on the line is the same distance from AB as CD X D B
Locus of points related to Two Fixed Lines
Equidistant to2 lines
Closer to line AB than CD

11. Locus of Points Closer to Line AB than Line CD. (click once to start)
1. Bisect the angles
2. Then shade the area on AB’s side of the angle bisectors C
3. Make the lines dashed if they are not included in this set of points – consider the wording of the problem carefully X D B
Locus of points related to Two Fixed Lines
Equidistant to2 lines
Closer to line AB than CD

12. Notes and Exercises Copy Notes from Gamma pages
Do locus exercise together
Then finish of pages 69 and 70 your workbook.