00:01
Okay, so let's determine if this following identity is true.
00:06
So let's start with our left -hand side.
00:07
So we have cosine minus cosine.
00:09
Let's rewrite that as a product.
00:11
So we have, that is, we have a negative 2, sine of 2 plus 4 over 2.
00:21
So that's a 6 over 2, which is a 3x.
00:26
And then sign of 2x minus 4x, that's a negative 2x over 2.
00:33
So that's an x or a negative x.
00:35
We can pull out that negative sign, so we get a plus here.
00:39
And that's to the power of 2.
00:42
Plus, well, let's use our sum to product again...