Let a → , b → and c → be three vectors such that a → = 3 , b → = 5 , b →…

Let a→,b→ and c→ be three vectors such that a→=3,b→=5,b→∙c→=10 and the angle between b→ and c→ is π3. If a→ is perpendicular to the vector b→×c→, then a→×b→×c→ is equal to ____________.

Solution

b→.c→=10⇒b→c→cos⁡π3=10⇒5.c→.12=10

⇒c→=4

Also, a→.b→×c→=0

a→×b→×c→=a→b→×c→sin⁡π2

⇒3×b→c→sin⁡π3×1

⇒3×5×4×32=30

Asked in: JEE Main 2020 (09 Jan Shift 2)

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