$$\int \frac{x^3 \sin \left(\tan ^{-1}\left(x^4\right)\right)}{1+x^8} d x$$ is equal to

The value of $$\int \frac{x^2 d x}{\sqrt{x^6+a^6}}$$ is equal to

The value of $$\int \frac{x e^x d x}{(1+x)^2}$$ is equal to

The value of $$\int e^x\left[\frac{1+\sin x}{1+\cos x}\right] d x$$ is equal to