Deletion of Sine

Comment: There's lots here that's not in Trigonometric_functions#Sine.2C_cosine_and_tangent, and there's a lot more that can be said about sines than just the definition. Some is in other articles (e.g. List of trigonometric identities), but this is still a useful and encyclopedic topic. It's a |bad argument to say "there's no article on cosines so we should delete the article on sines": this is a wiki, and articles aren't created according to a careful plan. Maybe we need an article on cosines. Plus, if you're going to propose a redirect (a) do it on Wikipedia:Redirects for discussion not here, and (b) say what you think it should actually redirect to
Stance: keep
Cited policy: Wikipedia:Arguments to avoid in deletion discussions (WP:OSE)