Compare the results of using Equations (4) and (5)
Equations (4) and (5) lead to different formulas for the integral of $\tan ^{-1} x$
$$\text { a. } \int \tan ^{-1} x d x=x \tan ^{-1} x-\ln \sec \left(\tan ^{-1} x\right)+C$$
$$\text { b. } \int \tan ^{-1} x d x=x \tan ^{-1} x-\ln \sqrt{1+x^{2}}+C$$
Can both integrations be correct? Explain.