Page 88 - Start Up Mathematics_6

7. Three or more lines are said to be concurrent if they pass through the same point.

8. A ray is part of a line which extends endlessly in one direction and has one end point.
9. A plane is a smooth flat surface extending indefinitely in all directions.

10. The figures having different beginning and end points are called open figures and figures
having the same beginning and end points are called closed figures.
11. A curve that does not cross itself is called a simple curve.

12. A polygon is a simple closed figure made up of line segments.
13. An angle is a figure formed by two rays with the same initial point. The initial point is called
the vertex and the rays are called the arms of the angle. Its measure is the rotation through
which one ray undergoes to reach the other.
14. A three-sided polygon is called a triangle and quadrilateral is a four-sided polygon.

15. A circle is a set of points in a plane equidistant from a fixed point. The fixed point is known
as centre and the constant distance is the radius.
16. A line segment joining two points on a circle is called a chord of the circle.

17. A line passing through two points on a circle is called a secant.
18. A region enclosed by an arc of a circle and its corresponding chord is called a segment.
19. The circumference of the circle is the length of its outer boundary.

20. A diameter divides a circle into two equal parts, each a semicircle.

21. A region enclosed by two radii and an arc is called a sector.
22. Circles having the same centre are called concentric circles.

Review Exercises

Multiple ChoiCe Questions
1. The vertex of an angle lies:

(a) in its interior (b) in its exterior (c) on the angle (d) none of these
2. A point on the midpoint of the radius of a circle lies in its:

(a) interior (b) exterior (c) boundary (d) none of these
3. The number of straight lines passing through one point are:

(a) 1 (b) 2 (c) 3 (d) infinite
4. The number of ray(s) starting from one given point and passing through another fixed point is:
(a) 1 (b) 2 (c) 3 (d) infinite

5. The number of common point(s) in semicircles formed on either side of the diameter is:
(a) 0 (b) 1 (c) 2 (d) infinite

6. A plane can be determined by:
(a) 1 point (b) 3 collinear points

(c) 3 non-collinear points (d) 4 collinear points

80