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If veca and vecb are two non collinear u...

If `veca` and `vecb` are two non collinear unit vectors and `iveca+vecbi=sqrt(3)` then find the value of `(veca-vecb).(2veca+vecb)`

Text Solution

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The correct Answer is:
`(1)/(2)`
`because a=b = 1` so `a^(2) + b^(2) + 2ab cos theta = (sqrt3)^(2) = 3`
`rArr " "1+1 + 2cos theta = 3 rArr cos theta = (1)/(2)`
`( veca-vecb) *( 2veca+ vecb) = 2a^(2) - b^(2) - abcostheta`
`" "= 2-1- (1)/(2 )=(1)/(2)`
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