**Ex 10.2, 18**

Last updated at Dec. 8, 2016 by Teachoo

Last updated at Dec. 8, 2016 by Teachoo

Transcript

Ex 10.2, 18 In triangle ABC (Fig 10.18),which of the following is not true (A) π΄π΅ο·― + π΅πΆο·― + πΆπ΄ο·―= 0ο·― (B) π΄π΅ο·― + π΅πΆο·― β π΄πΆο·―= 0ο·― (C) π΄π΅ο·― + π΅πΆο·― β πΆπ΄ο·―= 0ο·― (D) π΄π΅ο·― β πΆπ΅ο·― + πΆπ΄ο·―= 0ο·― In Ξ ABC, π΄πΆο·― is the resultant of π΄π΅ο·― & π΅πΆο·― π΄πΆο·― = π΄π΅ο·― + π΅πΆο·― π΄π΅ο·― + π΅πΆο·― = π΄πΆο·― π΄π΅ο·― + π΅πΆο·― β π΄πΆο·― = 0ο·― Checking part (A) π¨π©ο·― + π©πͺο·― + πͺπ¨ο·―= πο·― From (1) π΄π΅ο·― + π΅πΆο·― β π΄πΆο·― = 0ο·― π΄π΅ο·― + π΅πΆο·― β (β πΆπ΄ο·―) = 0ο·― π΄π΅ο·― + π΅πΆο·― + πΆπ΄ο·― = 0ο·― Hence, (A) is true. Checking part (B) π¨π©ο·― + π©πͺο·― β π¨πͺο·―= πο·― From (1) π΄π΅ο·― + π΅πΆο·― β π΄πΆο·― = 0ο·― Hence, (B) is true. Checking part (C) π¨π©ο·― + π©πͺο·― β πͺπ¨ο·―= πο·― From (1) π΄π΅ο·― + π΅πΆο·― β π΄πΆο·― = 0ο·― π΄π΅ο·― + π΅πΆο·― β (β πΆπ΄ο·―) = 0ο·― π΄π΅ο·― + π΅πΆο·― + πΆπ΄ο·― = 0ο·― Hence, (C) is not true. Checking part (D) π¨π©ο·― β πͺπ©ο·― + πͺπ¨ο·―= πο·― From (1) π΄π΅ο·― + π΅πΆο·― β π΄πΆο·― = 0ο·― ABο·― β CBο·― + CAο·― = 0ο·― Hence, (D) is true. Thus, (C) is the correct option

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He provides courses for Mathematics from Class 9 to 12. You can contact him here.