I think it could still use some cleanup  First some of the terms used for identities do match the terms used for the same identities on the List of trigonometric identities page  Ideally I think this page should match that one with the proofs linked between sections  Also the typesetting of the formulae does not match  Look at the equations in the angle sum section for details  Finally there is inconsistent layout between sections  For example the Eulerian proof in the Angle sum section is thrown in to the sum section  It seems to me it should really have its own at least sub header to separate it as is done for other identities on the page