You just need a counter-example? Many examples work really. Chances are if you pick a random value for x off the top of the head, you would have a counter example. For example, :
I'm taking my last class for my bachelors and of'course it's my worst class, trigonometry.
Can anybody help me with this problem?
"Show the counter example that the following equation is not an identity?"
(sin x+ cos x)2=sin2x+cos2x (The "2"s are squares)
Thanks for the help!