If a → , b → , c → are vectors such that a → + b → + c → = 0 and a → = 7 , b → = 5 , c → = 3 then angle between vector b → and c → is

Question

If a → , b → , c → are vectors such that a → + b → + c → = 0 and a → = 7 , b → = 5 , c → = 3 then angle between vector b → and c → is, 60 °, 30 °, 45 °, 90 °

MARKS App · Accepted Answer

Given a → + b → + c → = 0 ⇒ b → + c → = - a → ⇒ b → + c → 2 = - a → 2 ⇒ b → 2 + c → 2 + 2 b → · c → = a → 2 Let M be the angle between b → and c → ⇒ 25 + 9 + 2 * 5 * 3 cos M = 49 ⇒ cos M = 1 2 ⇒ M = 60 °

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