.If ifference of two unit vectors is a unit vector, prove that magnitude of their sum is `sqrt3`

Explanation

`| vec a| = 1, | vec b|=1`

`| vec a - vec b | = 1`

`sqrt( a^2 + b^2 - 2 vec a vec b cos theta) = 1`

`sqrt(1 + 1 - 2*1*1*cos theta) = 1`

`1 + 1 - 2 cos theta = 1`

`2cos theta = 1`

`cos theta = 1/2`

`|vec a + vec b| = | vec a|^2 + |vec b|^2 + 2|vec a|| vec b| cos theta`

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