dsolve({diff(diff(x(t),t),t) = a*exp(2*x(t))-exp(-x(t))+exp(-2*x(t))*cos(y(t))^2, diff(diff(y(t),t),t) = exp(-2*x(t))*sin(y(t))*cos(y(t))-sin(y(t))/cos(y(t))^3})