documentclass{article}
usepackage{lipsum}
everymath{displaystyleallowbreak}
linespread{2.0}

begin{document}

lipsum[1]
$frac{1}{c_s^{2}} partial_{t}{psi_{1}}
partial_{t}{rho_{0}}+frac{1}{c_s^{2}} partial_{t}{rho_{0}}
partial_{i}{psi_{1}} v^{(0)}_{i}+frac{1}{c_s^{2}}
partial_{t}{partial_{t}{psi_{1}}} rho_{0}+frac{1}{c_s^{2}}
partial_{t}{v^{(0)}_{i}} partial_{i}{psi_{1}}
rho_{0}+frac{1}{c_s^{2}} partial_{t}{partial_{i}{psi_{1}}}
rho_{0} v^{(0)}_{i}+frac{1}{c_s^{2}} partial_{t}{psi_{1}}
partial_{i}{rho_{0}} v^{(0)}_{i}+frac{1}{c_s^{2}}
partial_{i}{partial_{t}{psi_{1}}} rho_{0}
v^{(0)}_{i}$
lipsum[1]
end{document}