can u put this equation in function of $H$ : $T = \sqrt{h_{1}^2 - H^2}+\sqrt{h_{2}^2 -H^2}$ can u put this equation in function of H : 
$$T = \sqrt{h_{1}^2 - H^2}+\sqrt{h_{2}^2 -H^2}$$
to:
H = something...
$T$ and $H$ are variables, and $h_1$ and $h_2$ are constants
thank u all
:D

$$T=\sqrt{h_1^2-H^2}+\sqrt{h_2^2-H^2}\\(T-\sqrt{h_1^2-H^2}=\sqrt{h_2^2-H^2})^2\\T^2+h_1^2-H^2-2T\sqrt{h_1^2-H^2}=h_2^2-H^2\\
T^2+h_1^2-h_2^2=
+2T\sqrt{h_1^2-H^2}\\
\sqrt{h_1^2-H^2}=\frac{T^2+h_1^2-h_2^2}{2T}$$ go to the power of two again ,and find $H^2$
$$h_1^2-H^2=(\frac{T^2+h_1^2-h_2^2}{2T})^2\\
h_1^2-(\frac{T^2+h_1^2-h_2^2}{2T})^2=H^2\\\to
H=\pm \sqrt {h_1^2-(\frac{T^2+h_1^2-h_2^2}{2T})^2}$$
