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2) Ruler and compasses constructions
 Use ruler, only to draw lines, and compasses, only to draw arcs.
 Be careful while doing these constructions.
 Here are some tips for construction.
(a) Draw thin lines and mark points lightly.
(b) Maintain instruments with sharp tips and fine edges.
(c) Have two pencils in the box, one for insertion into the compasses and the other to
draw lines or curves and mark points.

3) The Circle and construction of a circle when its radius is known

CIRCLE: It is a closed 2-D shape whose very point on its boundary is at an equal
distance from its centre.
To construct: A circle when its radius is known

For example: To construct a circle of radius 3 cm using compasses.

Steps of construction:

Step 1: Open the compasses for the required radius of 3cm.
Step 2: Mark a point with a sharp pencil where we want the centre of the circle to be.
Name it as O.

Step 3: Place the pointer of the compasses on O.

Step 4: Turn the compasses slowly to draw the circle. Be careful to complete
the movement around in one instant.