I have to show that 2-form ω= sin α dα ∧ ds is well defined on the phase space of an ellipse which can be topologically seen as a cylinder with α∈(0,π) the angle of an oriented line going inwards and s∈ℝ/Lℤ the arc-length parameter. How can I proceed to prove that the 1-forms are well defined ?
Thank you in advance.