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Question
Describe completely the locus of a point in the following case:
Centre of a circle of radius 2 cm and touching a fixed circle of radius 3 cm with centre O.
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Solution

The locus is a concentric circle (in red) of radius 1 cm if the circles touch internally and a concentric circle (in red) of radius 5 cm if the circles touch externally.
RELATED QUESTIONS
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Ruler and compass only may be used in this question. All construction lines and arcs must be clearly shown, and be of sufficient length and clarity to permit assessment.
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Given ∠BAC (Fig), determine the locus of a point which lies in the interior of ∠BAC and equidistant from two lines AB and AC.
