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Construct a circle of radius 4 cm, passing through a given point C and touching a straight line AB.
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1. Draw two straight lines parallel to the given straight line AB at the distance of 4 cm from the given line.
It is one of the basic geometry construction problems.
2. Draw the circle of the radius of 4 cm with the center at the given point.
3. The intersection points of this circle with (one/any of) the two parallel lines (if exists) will be the center of the circle you are looking for.
The word "Describe", the first word in your condition, is not appropriate for this geometry problem.
It makes it a literature problem instead of a geometry problem.
To make it a geometry problem, use the term "Construct" instead of "Describe".