1. This conclusion is incomplete. The greater the dip angle at (0,90), the greater the slope, and the greater the dip angle at (90, 180), the greater the slope, but they cannot be said together.

2.k can be negative.

3.y'=2x, the slope of the derivative function is equal to 2, and the inclination angle is equal to arctan2, which is a fixed value.

We say that the angle is steep, but we should pay attention to the fact that the scope of discussion is divided into two parts: acute angle and right angle.