Euler Form of `S^2`
Nov 9 2017
The following code calculates the Euler form of `S^2`.
`e(TS^2) = 1/(4pi) (Omega_(i_2)^(i_1) - Omega_(i_1)^(i_2))``omega'_l^i = (a^-1)_j^i omega_k^j a_l^k + (a^-1)_j^i da_l^j`
`omega' = a^-1 omega a + a^-1 da`
`omega = a^-1 omega_0 a + a^-1 da`