If `veca and vecb` are two vectors of magnitude 1 inclined at `120^(@)`, then find the angle between `vecb and vecb-veca`.

Explanation

`|veca|= |vecb|=1`
Hence, vectors `veca and vecb` are adjacent sides of rhombus `OACB`
Angle between `veca and vecb` is `120^(@)`.
Also diagonals of rhombus are OC and AB. Thus,
`" "vec(OC)= veca+vecb and vec(AB)= vecb-veca`
Clearly from the figure, angle between `vecb and vecb-veca` is `30^(@)`.
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