Page 55 - Ganit Kaushal

(j) The unit of measurement of the magnitude of an angle is _______ .

(k) An angle greater than 180° and less than a complete angle is called _______ .
(l) The number of right angles in a straight angle is _______ and that in a complete angle
is _______ . (NCERT Exemplar)

(m) The number of angles less than 180° in the
given figure (i) is _______ and their names
are _______ . (NCERT Exemplar)
(n) The number of straight angles in the given
figure (i) is _______ . (NCERT Exemplar)
(o) The number of common points in the two
angles marked in the adjoining figure (ii) is
_______ . (NCERT Exemplar) (i) (ii)
Sol. (a) 2; The common points in the two angles ∠BAC and ∠EDF are P and O.
(b) straight (c) right (d) reflex (e) complete

(f) straight angle (g) acute angle (h) obtuse angle (i) right angle
(j) degree (k) reflex angle (l) 2; 4
(m) 12; ∠OAB, ∠OBA, ∠OAC, ∠OCA, ∠OCD, ∠ODC, ∠AOB, ∠AOC, ∠COD, ∠DOB, ∠BAC,
∠ACD.
(n) 4 (o) 4, (namely D, E, F, G)
Ex 18. State whether the following statements are True (T) or False (F).
(a) Two lines or line segments are perpendicular if they form a right angle.

(b) Only one line can pass through a given point.
(c) Two angles can have exactly five points in common.
(d) The line segment AB is the shortest route from A to B (figure (iii)).
(e) A line cannot be drawn wholly on a sheet of paper.
(f) A line segment is made up of an infinite number of points.
(iii)
(g) Two lines in a plane always intersect.
(h) Two different lines can be drawn passing through two distinct points.

(i) In the figure (iii), C is a point on the ray BD.
(j) A figure formed by two rays with the same initial point is known as an angle.
(k) A horizontal line and a vertical line always intersect at right angles. (NCERT Exemplar)
(l) If the arms of an angle on the paper are increased, the angle increases. (NCERT Exemplar)
(m) If the arms of an angle on the paper are decreased, the angle decreases. (NCERT Exemplar)

(n) Two line segments may intersect at two points. (NCERT Exemplar)
Sol. (a) True (b) False ( infinite lines can pass)
(c) False ( 1 or more than 1 point in common) (d) True
(e) True (f) True (g) False ( they can be parallel)

(h) False ( only one line can be drawn) (i) True (j) True
(k) True (l) False ( it remains the same)

(m) False ( it remains the same) (n) False ( they can intersect only at one point)

Lines and Angles 53