Locus — Revision Notes
ICSE · Class 10 · Mathematics
Locus revision notes for ICSE Class 10 Mathematics: 4 topics in quick points. Part of the ICSE Class 10 Mathematics syllabus.
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1. Core Idea of Locus
- The locus of a moving point is the path traced under the given condition.
- Every point which satisfies the given conditions lies on the locus.
- Every point which lies on the locus, satisfies the given condition(s).
2. Theorem 1: Points Equidistant from Two Fixed Points
- The locus of a point equidistant from two given points is the perpendicular bisector of the line segment joining the two points.
- This theorem is tested separately from the theorem about intersecting lines.
- If P satisfies PA = PB, then P lies on the perpendicular bisector of AB.
3. Theorem 2: Points Equidistant from Two Intersecting Lines
- The locus of a point equidistant from two intersecting lines is the pair of lines bisecting the angles between the lines.
- The pair of lines is X'OX and Y'OY, not a single line.
- If P is equidistant from the two lines, then P lies on one of the angle bisectors.
4. Standard Locus Cases
- The locus of a point which is equidistant from two parallel straight lines is a straight line parallel to the given lines and mid-way between them.
- The locus of a point which is at a given distance from a given straight line consists of a pair of straight lines parallel to the given line and at a given distance from it.
- The locus of the centre of a wheel, which moves on a straight horizontal road, is a straight line parallel to the road and at a distance equal to the radius of the wheel.
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