... computes.¹

We will derive this expression on the last day of class, if there is time. You may verify for yourself that if $\vec f$ is constant, this reduces to your current expression.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.