00:01
We're asked to find the inverse's derivative at the c value of negative 1⁄2.
00:09
So you really need a good background understanding with the function they give you, which is the sign curve.
00:19
And we only care between negative pi over 2 to positive pi over 2.
00:27
And the reason why we have those bounds is because, well, if we take the derivative of sign, which is cosine, and we consider from negative pi over 2 to positive pi or 2.
00:42
So remember on the unit circle, that negative pi over 2 is down this way, and positive pi or 2 is up here.
00:48
If we didn't have these bounds, then cosine of x would not be positive everywhere.
00:52
Because remember, cosine is the x coordinates, and cosine is always positive in there and there.
00:58
So if the derivative is always positive, then the function is always increasing...