Interesting. I'm helping my sister with Differential Calculus this semester. I made her calculate the rate of change of Sin(x) between different sets of points

Interesting. I'm helping my sister with Differential Calculus this semester. I made her calculate the rate of change of Sin(x) between different sets of points for her to see that it can have different values if the "traditional" rate of change rule is applied. It's then easier to justify the derivative concept of "slope at every point".