Let a vertical tower $A B$ of height $2 h$ stands on a horizontal ground. Let from a point $P$ on the ground a man can see upto height $h$ of the tower with an angle of elevation $2 \alpha$. When from $P$, he moves a distance $d$ in the direction of $\overrightarrow { A P }$, he can see the top $B$ of the tower with an angle of elevation $\alpha$. If $d = \sqrt { 7 } h$, then $\tan \alpha$ is equal to (1) $\sqrt { 5 } - 2$ (2) $\sqrt { 3 } - 1$ (3) $\sqrt { 7 } - 2$ (4) $\sqrt { 7 } - \sqrt { 3 }$
Let a vertical tower $A B$ of height $2 h$ stands on a horizontal ground. Let from a point $P$ on the ground a man can see upto height $h$ of the tower with an angle of elevation $2 \alpha$. When from $P$, he moves a distance $d$ in the direction of $\overrightarrow { A P }$, he can see the top $B$ of the tower with an angle of elevation $\alpha$. If $d = \sqrt { 7 } h$, then $\tan \alpha$ is equal to\\
(1) $\sqrt { 5 } - 2$\\
(2) $\sqrt { 3 } - 1$\\
(3) $\sqrt { 7 } - 2$\\
(4) $\sqrt { 7 } - \sqrt { 3 }$