If a → = 2 , b → = 5 and a → × b → = 8 , then a → · b → is…

If a→=2,b→=5 and a→×b→=8, then a→·b→ is equal to:
  1. 6
  2. 4
  3. 3
  4. 5

Solution

We have, a→=2,b→=5 

and a→×b→=8

Now, a→×b→=a→b→sinθ=8

⇒sinθ=±45

∴ a→·b→=a→b→cosθ

=10.±35=±6

⇒a→·b→=6.

Asked in: JEE Main 2021 (25 Jul Shift 2)

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