The position vectors of vertices of tria...

The position vectors of vertices of `triangle ABC` are `(1, -2), (-7,6) and (11/5, 2/5)` respectively. The measure of the interior angle A of the `triangle ABC,` is,

A

acute and lies in `(75^(@), 90^(@))`

B

acute and lies in `(60^(@), 75^(@))`

C

acute and lies in `(45^(@), 60^(@))`

D

obtuse and lies in `(120^(@), 150^(@))`

Verified by Experts

The correct Answer is:

B

`tan(theta_(2)-theta_(1))=(m_(2)-m_(1))/(1+m_(1)m_(2))=((8)/(-6)-2)/(1-(16)/(6))`

`tan theta=(20)/(10)=2`

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