Hi I'm having some problems seeing how they've come to an answer in the course book, here we go. and then through several stages, some skipped, we get Any help would be appreciated. Thanks
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look here Some formulae may be helpfull
use cos2x formula
------------------------------------------ sorry for the long explanation :P EDIT: just realized this wasn't really about proving the equalities.. meh I'll leave it unedited anyways )
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