Unit- 5 Lines and Angles corrected

1 An angle is formed when two Lines or rays or line segments meet orintersect. When the sum of the measures of two Angles is 90 , the Angles arecalled complementary Angles . Each of them is called complement ofthe other. When the sum of the measures of two Angles is 180 , the Angles arecalled supplementary Angles . Each of them is called supplement ofthe other. Two Angles are called adjacent Angles , if they have a common vertexand a common arm but no common interior points. A linear pair is a pair of adjacent Angles whose non-common sidesare opposite rays. When two Lines intersect, the vertically opposite Angles so formedare equal.

2 When two Lines are intersected by a transversal, eight Angles areformed. These Angles can be classified as 4 interior Angles , 4 exteriorangles, 4 pairs of corresponding Angles , 2 pairs of alternate interiorangles, 2 pairs of alternate exterior Angles and two pairs of interiorangles on the same side of the transversal. If two parallel Lines are intersected by a transversal,(i)each pair of corresponding Angles is equal.(ii)each pair of alternate interior Angles is equal.(iii)each pair of interior Angles on the same side of the transversal issupplementary. Converses of the above results are also In each of the Examples 1 to 4, there are four options, out of which oneoption is correct.

3 Write the correct 1:The Angles between North and East and North and Westare(a)complementary Angles (b)supplementary Angles (c)both acute Angles (d)both obtuse anglesSolution:Correct answer is (b).Example 2:Which of the following pair ofangles are supplementary?(a)48 , 42 (b)60 , 60 (c)75 , 105 (d)179 , 2 A point name a line is perfectly straight and extendsfor ever in both plane is a perfectly flat surface thatextends forever in all segment, or line segment, is the partof a line between two ray is part of a line that starts atone point and extends for ever in A line e, or plane p, or plane DEFFig. Solution:Correct answer is (c).

4 Example 3:In Fig. , a pair ofcorresponding Angles is(a) 1, 2(b) 3, 6(c) 3, 5(d) 3, 7 Solution:Correct answer is (d).Fig. 4:If two Lines are intersected by a transversal, then thenumber of pairs of interior Angles on the same side ofthe transversal is(a)1(b)2(c)3(d)4 Solution:Correct answer is (b).In Examples 5 to 7, fill in the blanks to make the statements 5 :Two Lines in a plane which never meet at any point arecalled :parallel linesExample 6: Angles of a linear pair are _____ as well as _____ .Solution:adjacent, supplementaryExample 7:Adjacent Angles have a common vertex, a common_____ and no-common :arm, interior pointsAn angle ( ) is formed by two rays with a common endpoint called thevertex (plural, vertices).

5 Angles can be measured in degrees, m l meansthe measure of 1. The Angles can be named XYZ, 1, or Y. The vertexmust be the middle In Examples 8 to 11, state whether the statements are True or 8:Sum of two complementary Angles is 180 .Solution:FalseExample 9:Sum of two supplementary Angles is 180 .Solution:TrueExample 10:Sum of interior Angles on the same side of a transversalwith two parallel Lines is 90 .Solution:FalseExample 11:Vertically opposite Angles are :TrueExample 12: In Fig. , four linesegments PQ, QR, RSand ST are making theletter W, PQ||RS andQR||ST. If angle betweenPQ and QR is 39 , findthe values of x and :Since PQ||RS and QR istransversal, so x = 39 [Alternate interior Angles ]Again QR||ST and RS is a , y = x[Alternate interior Angles ]or y = 39 Example 13:In Fig.

6 , are the Angles 1and 2 of the letter N forminga pair of adjacent Angles ?Give :No, 1 and 2 are not forminga pair of adjacent Angles as theydo not have a common 14:In Fig. , the points A, O andB are collinear. Ray OC ray OD. Check whetherFig. (i) AOD and BOCare complementary,(ii) AOC and BOC :Since points A, Oand B are collinear(Given), therefore ABis a straight line.(i)As O is a point on the line AB, therefore AOD + DOC + BOC = 180 or, AOD + BOC + 90 = 180 or, AOD + BOC = 90 So, AOD and BOC are complementary Angles .(ii)Also, AOC and BOC are supplementary as AOC + BOC = 180 Example 15:In Fig.

7 AB||EF, ED||CBand APE is 39 . Find :Since ED||BC and AB is atransversal, soso QBP = APE[Corresponding Angles ]or QBP = 39 Now,AB||EF and BC is , FQB = QBP[Alternate interior Angles ]Fig. right angle measures 90 . An acute angle measures greater than 0 andless than 90 . An obtuse angle measures greater than 90 and less than180 . Complementary Angles are two Angles whose measures add to 90 .Supplmentary Angles are two Angles whose measures add to 180 .15-04-2018 or FQB = 39 Also, CQF + FQB = 180 [Linear pair]So CQF + 39 = 180 or CQF = 180 39 or CQF = 141 Example 16:Out of a pair of complementary Angles , one is two-thirdof the other.

8 Find the :Let one angle be , other angle = 90 xThus, 23 x = 90 xor 2x = 270 3xor 2x + 3x = 270 or 5x = 270 or x = 270 5 = 54 So, one angle = 54 and the other angle = 90 54 = 36 .Example 17:In Fig. , CD intersects the line AB at F, CFB = 50 and EFA = AFD. Find themeasure of :Let EFA = AFD = is given that CD intersectsline AB at , CFB = AFD(Vertically opposite Angles )So,x = 50 But EFA = AFD which gives EFA = 50 Fig. figures have the same size and same shape. Segments that have the same length are congruent. Angles that have the same measure are congruent. The symbol for congruence is , which is read as is congruent to.

9 15-04-2018 Now CFB + EFA + EFC = 180 [As AB is a straightline].or,50 + 50 + EFC = 180 or, EFC = 180 100 Thus, EFC = 80 . which statements are correct: If X and Y are congruent,a. X = Y b. m X = m Y c. X why vertically opposite Angles must always be congruent. Solution: Understand and Explore the Problem What information is given in the question? Lines AB and CD are intersecting three Lines EF, GH and KPat distinct points forming Angles 1= 1230, 2 = 570, 3 = 550and 5 = 1220. What are you trying to find?We are trying to find(a)EF || GH or notFig. 18In the given figure, find out which pair of Lines (b)GH || KP or not(c)EF || KP or not(d)AB || CD or not Plan a Strategy(a)Since we want to find whether the Lines are parallel or not,therefore recall the conditions when the Lines are Lines are parallel if it satisfies any one of the following,(1)when corresponding Angles are equal(2)when alternate interior Angles are equal(3)when the sum of interior Angles on the same side ofthe transversal is 180.

10 (b)Find out what type of Angles are formed by Lines EF, GH, KPtaking AB or CD as transversal. Solve For Lines EF and GH, taking CD as transversal, 1 and 2are interior Angles on the same side of the , we check whether the sum of 1 and 2 is 180 ornot. 1 = 123 , 2 = 57 , 1 + 2 = 123 + 57 = 180 Since the sum of interior s on the same side of thetransversal is 180 , therefore EF || GH. For Lines GH and KP, taking CD as transversal, 2 and 3are corresponding s. If these Angles are equal, then linesare parallel. 2 = 57 , 3 = 55 2 3. Since corresponding Angles are not equal,therefore, GH is not parallel to KP. Similarly, for Lines EF and KP, taking CD as transversal 1 and 3 are interior Angles on the same side of thetransversal.