Question

Is cos(xy) the same as cosxcosy?

Answer 1

no

Answer 2

No. in cos(xy) you multiply degrees, but in the second one u multiply values

Answer 3

No. \[\cos(x)\cos(y) = {\cos(x-y) + \cos(y-x) \over 2}\]

Answer 4

Sorry. \[\cos(x)\cos(y) = {\cos(x-y) + \cos(x+y) \over 2}\]