And the point is that the second derivative of A, with respect to V and T in this order is the same as the second derivative of a with respect to T and V in this order. 问题的关键在于A的二阶导数("),对V和T以这样一个顺序求导,和对T和V以这样一个顺序,求导是一样的。
Basically, the answer for us is that we don't have a second derivative test in this situation. 基本上,答案就是,我们不可以用二次导数来验证这个情况。
So, it's the second derivative of a position vector. 它是位置向量的二阶导。
But when it comes to the second derivative you have to see how alpha is changing. 然而对于二阶导数("),就得看α的变化规律了。
And all we did, further, is take that second derivative. 总而言之,我们所做的就是求二阶导数(")。