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prove that

Use these formulas: and

Quote: Originally Posted by red_dog Use these formulas: and thanks, but I have never seen these formula's or been taught them. where did you get them from? surely If I needed to use these formula's It would be in the book, that the question is from?

Quote: Originally Posted by Tweety thanks, but I have never seen these formula's or been taught them. where did you get them from? surely If I needed to use these formula's It would be in the book, that the question is from? Prove that Hi Tweety, I don't know what formulas you have been taught, but here's another proof using the Tan sum formula: . Now, distribute: You know that