Given that \(a\) is a non-zero constant, which of the following integrals is equal to zero?
- \(\displaystyle \int_{-a}^a x\, \cos ^{-1}(x) d x\)
- \(\displaystyle\int_{-a}^a x^2\, \cos ^{-1}(x) d x\)
- \(\displaystyle\int_{-a}^a x\, \tan ^{-1}(x) d x\)
- \(\displaystyle\int_{-a}^a x^2\, \tan ^{-1}(x) d x\)