Homework Help: Prove or Disprove

Posted by Jerry on Tuesday, November 13, 2012 at 11:01am.

Cos(X+y)cos(x-y)= cos^2theta - sin^2theta

I foiled the left side as a start because I can kind of see sin^2+cos^2=1 but I can't finish.

Prove or Disprove - bobpursley, Tuesday, November 13, 2012 at 11:07am
It can't be proved....unless you know what relationship Theta has with x and y.

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