00:01
Some of my explanations might be a bit weird, but let me just give you an example.
00:07
Why sine of x plus sine of y equaling sine of x plus y is wrong.
00:16
So let me just identify that it's false first.
00:20
And the reason why it's false is let's just let x and y be the same thing, which is pi over two.
00:28
Well then if i do this first statement, hopefully you're aware of the unit circle, that's zero one and sine is the y coordinate.
00:38
So sine of pi over two is one and sine of pi over two is one, which equals two.
00:43
But over here we have to add pi over two with pi over two first, which takes me to this value and that ordered pair is negative one zero.
00:52
So this may i'll write that out real quick is sine of pi, which equals zero and that does not equal two.
01:04
So that's why that's false.
01:06
So it's just a counter example.
01:08
Now letter b, um, i had, i went and looked at our double angle formulas and what i looked at is a double angle formula for cosine.
01:24
So what they actually gave you is one minus two sine squared.
01:29
I'll double check looking at my formula sheet.
01:31
There it is...