Going from two to three, that's an adiabatic expansion, so q is equal to zero in that step.

从第二点到第三点，是绝热膨胀，因此q等于零。

麻省理工公开课 - 热力学与动力学课程节选

So now, then we're going to use what we're going to learn from step two in order to calculate III this part, what we could call step three.

现在我们要用从步骤II中,得知的东西来计算这个部分,我们可以叫它步骤。

麻省理工公开课 - 热力学与动力学课程节选