# P. 592, lines 11 and 12

${\displaystyle x(t+\Delta t)\approx x(t)+{\frac {\Delta t}{2}}\left[\left(-x^{3}(t)+\sin \left(tx(t)\right)\right)+\left(-\left(x(t)+f(x(t),t)\Delta t\right)^{3}+\sin \left((t+\Delta t)(x(t)+f(x(t),t)\Delta t)\right)\right)\right]}$