$$ \frac { -g }{ 2 }(\frac { d}{ v_ocos(α) })^2 + v_osin(α)\frac { d}{ v_ocos(α) }=h $$
im 2. Summanden vo kürzen und mit dem Hauptnenner multiplizieren gibt
$$ \frac { -gd^2 }{ 2} + v_o^2d^2sin(α)cos(α)=hv_o^2dcos(α)^2 $$
$$ v_o^2d^2sin(α)cos(α)-hv_o^2dcos(α)^2 = \frac { g d^2}{ 2} $$
$$ v_o^2(d^2sin(α)cos(α)-hdcos(α)^2) = \frac { g d^2}{ 2} $$
$$v_o^2 = \frac { g d^2}{ 2( d^2sin(α)cos(α)-hdcos(α)^2 )} $$
$$v_o =±\sqrt { \frac { g d}{ 2( dsin(α)cos(α)-hcos(α)^2 )} }$$