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Ex 10.2

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Ex 10.2, 18 (MCQ) Important You are here

Ex 10.2, 19 (MCQ) Important

Last updated at Aug. 11, 2021 by Teachoo

Ex 10.2, 18 In triangle ABC (Fig 10.18),which of the following is not true (A) (π΄π΅) β + (π΅πΆ) β + (πΆπ΄) β= 0 β (B) (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β= 0 β (C) (π΄π΅) β + (π΅πΆ) β β (πΆπ΄) β= 0 β (D) (π΄π΅) β β (πΆπ΅) β + (πΆπ΄) β= 0 β In Ξ ABC, (π΄πΆ) β is the resultant of (π΄π΅) β & (π΅πΆ) β (π΄πΆ) β = (π΄π΅) β + (π΅πΆ) β (π΄π΅) β + (π΅πΆ) β = (π΄πΆ) β (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β = 0 β Checking part (A) (π¨π©) β + (π©πͺ) β + (πͺπ¨) β= π β From (1) (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β = 0 β (π΄π΅) β + (π΅πΆ) β β (β(πΆπ΄) β) = 0 β (π΄π΅) β + (π΅πΆ) β + (πΆπ΄) β = 0 β Hence, (A) is true. Checking part (B) (π¨π©) β + (π©πͺ) β β (π¨πͺ) β= π β From (1) (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β = 0 β Hence, (B) is true. Checking part (C) (π¨π©) β + (π©πͺ) β β (πͺπ¨) β= π β From (1) (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β = 0 β (π΄π΅) β + (π΅πΆ) β β (β(πΆπ΄) β) = 0 β (π΄π΅) β + (π΅πΆ) β + (πΆπ΄) β = 0 β Hence, (C) is not true. Checking part (D) (π¨π©) β β (πͺπ©) β + (πͺπ¨) β= π β From (1) (π΄π΅) β + (π΅πΆ) β β (π΄πΆ) β = 0 β (AB) β β (CB) β + (CA) β = 0 β Hence, (D) is true. Thus, (C) is the correct option