4. ∠FCB ≅ ∠GDC: Corresponding angles theorem (when two parallel lines are crossed by a transversal, the corresponding angles formed are congruent) (but to use this, you have to state that ∠BCF and ∠CDG are corresponding)
5. ∠FCB ≅ ∠GCD: Subst. POC (Because ∠FCB ≅∠GDC and ∠GDC≅∠GCD)
6. Converse of the corresponding angles theorem
I can not really show my work since most proofs are theoretical and hence most work is done in the head.
