Question

if
|A×B|=√3A•B, then the value of |A+B| is
​

Answer 1

Explanation:

A×B=ABsinθ

Also, A.B=ABcosθ

Given : ∣A×B∣=

3

A.B

Using ∣A×B∣=∣A∣∣B∣sinθ

We get ∣A×B∣=ABsinθ

A.B=∣A∣∣B∣cosθ

∴ ABsinθ=

3

ABcosθ

tanθ=

3

⟹θ=60

o

Now (A+B)

2

=A

2

+B

2

+2A.B

=A

2

+B

2

+2ABcosθ

=A

2

+B

2

+2AB×

2

1

=A

2

+B

2

+AB

or ∣A+B∣=(A

2

+B

2

+AB)

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