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Last updated at March 22, 2023 by Teachoo

Example 18 If π β is a unit vector and (π₯ β β π β) β (π₯ β + π β) = 8 , then find |π₯ β| Given π β is a unit vector So, π β has a magnitude 1. β΄ |π β | = 1. Given that (π β β π β) β (π β + π β) = 8 π₯ β . π₯ β + π₯ β . π β β π β . π β β π β . π β = 8 π₯ β . π₯ β + π₯ β . π β β π β . π β β π β . π β = 8 π β . π β β π β . π β = 8 |π β |2 β |π β |2 = 8 |π₯ β |2 β 12 = 8 (Using: π₯ β . π β = π β . π₯ β ) |π₯ β |2 = 8 + 1 |π₯ β |2 = 9 |π₯ β | = Β± β9 |π₯ β | = Β± 3 Since magnitude is not negative, β΄ |π β | = 3