Thread: Obtain the forumal of cos( theta 1 + theta2).....
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Dec27-09, 05:42 PM   #9
 
Quote by tiny-tim View Post
why minus?

(what basic formula are you using ??)

cos ( θ+[tex]\phi[/tex]) = cos (θ)cos([tex]\phi[/tex]) - sin (θ)sin([tex]\phi[/tex])

Right ?

Hence, the minus.