Write the following in the simplest form:

1. tan(inverse){cosx / 1+sinx} given -pi/2 < x < pi/2
2. sin(inverse) { the whole root of x/1+x}
3. tan(inverse) {2 root x / 1-x}
4. tan(inverse) {3 a (square)x - x (cube) / a(cube) - 3ax(square)