OK, I apologize in advance for being "that guy" but I feel compelled to ask: are there any practical applications of this, in the sense of applications of the n

OK, I apologize in advance for being "that guy" but I feel compelled to ask: are there any practical applications of this, in the sense of applications of the normal calculus "derivative" (eg, slope / "rate of change"). That is, would I ever calculate this "derivative" to solve any kind of real world engineering problem or anything? Or does this serve solely in the realm of pure (theoretical) mathematics?