Chapter 17.2, Problem 2QC

Suppose r(t) = $\langle \text{t, 0}\rangle$, for a ≤ t ≤ b, is a parametric description of C; note that C is the interval [a, b] on the x–axis. Show that ∫_C f(x, y) ds = ${\displaystyle {\int }_a^{b}f(t,0)dt}$, which is an ordinary, single – variable integral introduced in Chapter 5.