Please help with proving theorem 1.4.5. All relevant theorems are attached.

Theorem 1.4.5 Let C be a directed, regular curve in R", and f a vector field on Rn that is integrable along C. Then f is integrable along -C, and f (x) . dr = - f(x) . dr. The proof of Theorem 1.4.5 uses the following. Proposition 1.4.1 If C is a directed, regular curve with parameterisation r : [a, b] - Rn, then U(s) = r(atb -s), s E [a, b] is an admissible parameterisation for -C