Chaps, help!! I am currently coaching a student for her GCSE exam and have come across a question which, although I believe that I may have the right answer, is still bugging me!! Would appreciate talking through it for my own piece of mind. If anybody is interested then I will need to scan the diagram in and email it to you. Essentially it is about trigonometric transformations in the form y=a-bcos(kt)+a am fairly sure that I have it sorted but would appreciate another input......