A swimmer wants to cross a river from point A to point B. Line AB makes an angle of 30^° with the flow of river. Magnitude of velocity of the swimmer…

A swimmer wants to cross a river from point A to point B . Line AB makes an angle of $\displaystyle 30^{\circ}$ with the flow of river. Magnitude of velocity of the swimmer is same as that of the river. The angle $\displaystyle \theta$ with the line AB should be \_\_\_\_$\displaystyle { }^{\circ}$, so that the swimmer reaches point $\displaystyle B$.