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P: 849
 Quote by tiny-tim No, √(1 - cos(θ - φ))/2 is correct. How did you reformulate P and Q for that?
 But I can't seem to find a simple manipulation for P and Q to get the second formula all I can find is (P dot e1)(Q dot e1) - (P dot e2)(Q dot e2) Where e1 = (1,0) and e2 = (0,1) Again the back of my book gives the expanded for of cos($$\phi$$ + $$\theta$$) so I don't even know what they are trying to say.
As I said previously.

Is there an easier way ?