Slide 2 Slide 3 The surface which is flat and plane is known as
plane surface. For example paper. A curve in the plane whose
starting point is also the end point and which has no other self-
intersections. A simple closed curve is also known as Jordan curve
Slide 4 SSimple closed curve made up of line segments is called
polygon. CURVES THAT ARE POLYGONS Example 1 CURVES THAT ARE NOT
POLYGONS Example 2 Slide 5 Number of sides or vertices
ClassificationSample of figure 3 Triangle 4 Quadrilateral 5
Pentagon 6 Hexagon 7 Heptagon 8 Octagon 9 Nonagon 10 Decagon Slide
6 A diagonal is a line segment connecting two non consecutive
vertices of a polygon. Slide 7 The polygon, in which all the
diagonals lie in interior is known as convex polygon. The polygon,
in which some diagonals lie in exterior is known as concave
polygon. Slide 8 TThe angle sum property of quadrilateral is 360. C
B D A The angle sum property of triangle is 180. We have divided a
quadrilateral into two triangles.So,180+180=360 Slide 9 Based on
the nature of the sides or angles of a quadrilateral, it gets
special names. Slide 10 PROPERTIES 1. A quadrilateral with each
pair of opposite side parallel. 2. Opposite sides are equal 3.
Opposite angles are equal. 4. Diagonals bisect each other. 5.
Adjacent angles are supplementary. Slide 11 PROPERTIES 1. All the
sides are equal. 2. All the angles are equal. 3. The diagonals
bisect each other. 4. Also a rectangle. Slide 12 PROPERTIES 1. The
opposite sides are equal. 2. Diagonals are equal. 3. Each of the
angle is right angle. 4. A parallelogram with a right angle. Slide
13 PROPERTIES 1. A parallelogram with sides of equal length. 2. All
the properties of parallelogram. 3. Diagonals are perpendicular to
each other. Slide 14 PROPERTIES A 1. A quadrilateral with exactly
two pairs of equal consec- B D utive sides. 2. The diagonals are
perpendic- ular to each other. C 3. One of the diagonal bisect the
other. 4. In the figure m B=m D but m A= m C Slide 15 PROPERTIES 1.
Trapezium is a quadrilateral with a pair of parallel sides ( NOTE:
The arrow marks indicate parallel lines) Slide 16
