Loci (Locus) | O Level Mathematics 4024 & IGCSE Mathematics 0580 | Detailed Free Notes To Score An A Star (A*)
- If you have to find the something at “x cm distance from a point” – also called equidistant from a point
- Insert a pencil in the compass
- Open it using the ruler to the same length
- Put it on the point
- Draw the angle inside the shape where the region must be for the same distance
- If you have to find the angle bisector
- Consider this image
- Put the compass on one of the points market in red
- Open it more than half the distant to the other red points
- More than half the distance is required because otherwise the cross won’t form
- Mark a small cross on the other side of A (A is already of the point)
- Then keeping it opened at the same length, place the compass on the other rend point
- DO NOT CHANGE HOW WIDE IT IS OPENED
- Mark the cross
- Draw the line from the A to the cross
- For equidistant from two points
- Do the same steps as mentioned above, but now make crosses on both sides
- See images below
- All other rules same about compass opening etc
- Do not lift the compass before making the mark on both sides of the line.
- Remember, it is perpendicular bisector which means the angle is 90 and it divides the the line in two equal parts.
Equidistant from a line
- Remember, a line is infinite, it has no end. A line segment has ends.
- If you get a question regarding equidistant from a line/ line segment, the first steps are the same. It would have given you a distance that has to be taken. Use your ruler at various distances to mark the point on both sides of the line/ line segment. Then join the points with a straight line on both sides.
- Now if this is a line segment, instead of a line, there is one extra step – you need to close the two sides as well.
- Open your compass by the given distance (5 cm in this case).
- Put it on one end of the segment and draw a semicircle that joins the line above and below it. Then do the same on the other end.












