Page 129 - classs 6 a_Neat

SEMICIRCLE The end points of a diameter of a circle divide the circle into two
equal parts; each part is called a semicircle. Practice Exercise 7.4
A diameter of a circle divides the circular region into two equal parts; each part is called a semicircular
region.
1. Make a point A on the paper. Keeping the point A as the centre, draw two circles with radii 2 and 4 cm. What
In the figure given below, both the shaded regions are semicircular regions. kind of circles do you get?
2.Draw a circle having a radius of 3 cm. Draw two longest chords in the circle such that they are perpen dicular
to each other. What will be their point of intersection known as?
3. Draw a circle having a radius of 2 cm and mark the centre. Draw the diameter and find its length.
4. Draw a circle having a radius of 3 cm. Draw a chord XY such that the circle is divided into a major segment
and a minor segment. In which segment does the centre of the circle lie? Draw a circle having a radius of 4 cm.
Divide it into two equal halves. What is the dividing line known as?
1. Distinguish between a line, a line segment and a ray using one figure.
2. How many times can two distinct non-parallel lines lying in the same plane intersect each other?
3. How many lines can be drawn from a given point in a plane?

ARC Any part of a circle is called an arc of the circle.
In the given figure, the arc ACB has been shown by the thick part and denoted by ACB .
If the arc of a circle is greater than a semicircle, it is called a major arc.
On the other hand, if the arc of a circle is less than a semicircle, it is called a minor arc.
Thus, in the given figure, arc ACB is the minor arc and arc ADB is the major arc.

SECTOR OF A CIRCLE The area bounded by an arc and the two radiijoining the endpoints of the arc
with the centre is called a sector.

If the sector is formed by a major arc, it is called a major sector. If the sector is formed by a minor arc, it is
called a minor sector. In the figure given below, OACB is a minor sector while OADB is the major sector.

CONCENTRIC CIRCLES Two or more circles with the same centre are called concentric circles.

1. The diameter is the longest chord of a circle.
2. The diameter is twice the radius. d = 2r
3. In a circle there is a minor segment and a major segment.
4. In a circle there is a minor sector and a major sector.
5. A circle can be divided into two equal semicircles.