· A polygon is a
closed plane figure made up of line segments.
· The number of
angles is equal to the number of sides.
Interior Angles of a Polygon
If n represents the number of sides of a polygon, then The sum of the interior angles of the polygon 
Each interior
 of an n-sided regular polygon  |
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Exterior Angles of a Polygon
Sum of the exterior angles of any polygon is  .
An exterior
of an n-sided regular polygon  |
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Perpendicular Bisector of a Line Segment
In the diagram, AB is the perpendicular bisector of
PQ at M.
·
M is the midpoint of PQ.
·
·
· Any point on
AB is equidistant from P and Q.
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Construction:
Step 1:
Taking P and Q as centres and a radius greater than half of
PQ, draw arcs above
and below PQ such that the arcs cut each other at A and B.
Step 2: Join A to B with a straight line,
bisecting PQ at M.
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Angle bisector
In the diagram, QC is the angle bisector of
 .
·
·
·
Any point on QC or QC produced is equidistant from
PQ and RQ.
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Construction:
Step 1:
With the compass point at the vertex Q and suitable radius, draw an arc
cutting
QP at A and QR at B.
Step 2:
Taking A and B as centres, and the same radius, draw arcs to cut
each other at C.
Step 3: Join Q to C with a straight line. | |
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