these are getting me mad... Please help me on this one: Establish the identity: $\displaystyle cos(\alpha+\beta) + cos(\alpha-\beta) = 2\cos\alpha\cos\beta$ Thanks in advance for your help!
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What identities are you allowed to apply to this exercise? Thank you!
Originally Posted by jpman these are getting me mad... Please help me on this one: Establish the identity: $\displaystyle cos(\alpha+\beta) + cos(\alpha-\beta) = 2\cos\alpha\cos\beta$ Thanks in advance for your help! Hi jpman, This is pretty straight forward if you use the sum and difference formulas of cosine. $\displaystyle \cos(\alpha \pm \beta)=\cos \alpha \cos\beta \mp \sin \alpha \sin \beta$
Originally Posted by masters Hi jpman, This is pretty straight forward if you use the sum and difference formulas of cosine. $\displaystyle \cos(\alpha \pm \beta)=\cos \alpha \cos\beta \mp \sin \alpha \sin \beta$ Dude, you rock. I totally missed the sum and difference formulas... Thanks a bunch!
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