Exercises 71 and 72 compare the results of using Equations $(4)$ and $(5)$
Equations $(4)$ and $(5)$ give different formulas for the integral of $\cos ^{-1} x :$
a. $\int \cos ^{-1} x d x=x \cos ^{-1} x-\sin \left(\cos ^{-1} x\right)+C$
b. $\int \cos ^{-1} x d x=x \cos ^{-1} x-\sqrt{1-x^{2}}+C$
Can both integrations be correct? Explain.