Question

Please help, another math problem! This is all the information it gives me!

Answer 1

$1 + cos(6x) = 1 + cos(3x + 3x)$
$= 1 + cos3x cos3x - sin3xsin3x$
$= 1 + cos^{2}(3x) - sin^{2}(3x)$
$= 1 + cos^{2}(3x) - (1 - cos^{2}(3x))$
$= 2cos^{2}(3x)$

Answer should be (A), to be honest.

Answer 2

I think the answer is A but I don't know for certain .