Let \(f(x) = 7\tan^8x+7\tan^6x-3\tan^4x-3\tan^2x\) for all \(x\in\left(-\dfrac{\pi}{2},\dfrac{\pi}{2}\right)\), then the correct expression(s) is (are)
1
\(\displaystyle \int_0^{\dfrac{\pi}{4}}xf(x)dx = \dfrac{1}{12}\)
2
\(\displaystyle \int_0^{\dfrac{\pi}{4}}f(x)dx = 0\)
3
\(\displaystyle \int_0^{\dfrac{\pi}{4}}xf(x)dx = \dfrac{1}{6}\)
4
\(\displaystyle \int_0^{\dfrac{\pi}{4}}xf(x)dx =1\)