Analytic l ∨ m = > l∧α
Prove that if l∨m,
∵l? α,m? α
∴l∥α (judgment theorem of line-plane parallelism)
l∩α≦& gt; l∑m
When L∧α, l and m are parallel or different.
∴l∥m is a necessary and sufficient condition for l∧α.