Furthermore, the chapter’s emphasis on — “What does the sign of the second derivative tell you about the shape of the profit curve?” — cultivates critical thinking that software cannot replace. Criticisms and Limitations No chapter is perfect. Some educators argue that Feliciano and Uy’s Chapter 10 focuses too heavily on geometric and physical applications (ladders, cones, boxes) at the expense of modern applications like marginal analysis in machine learning (gradient descent), or rates of change in biological systems (population dynamics, enzyme kinetics). The problems, while classic, can feel dated. A 2024 student might roll their eyes at “a conical tank filling with water” but find “a social media post going viral” as a related rates problem more engaging.
The section is particularly feared. One problem might involve a lighthouse rotating its beam, a moving ship, and the speed of the light spot along a shore — requiring implicit differentiation with respect to time, the chain rule, and trigonometric substitution all at once. Pedagogical Philosophy: Why It Works Chapter 10 exemplifies a teaching philosophy that prioritizes application over abstraction . Feliciano and Uy were writing for students who would become practitioners — civil engineers calculating beam deflections, electrical engineers analyzing rates of change in circuits, business students finding break-even points. The chapter does not spend pages proving the Mean Value Theorem (that appears earlier, in Chapter 4). Instead, it shows how to use derivatives to solve a concrete problem. Furthermore, the chapter’s emphasis on — “What does
The answer lies in what technology cannot do — at least not yet. A computer can differentiate $12x - 4x^2$, but it cannot look at a real-world scenario, identify the relevant variables, and translate the situation into a mathematical model. Chapter 10 trains exactly that skill: reading a word problem, drawing a diagram, defining variables, and setting up the equation. This is the essence of mathematical modeling , a skill invaluable in data science, engineering design, and operations research. The problems, while classic, can feel dated
Additionally, the chapter provides scant attention to or sensitivity analysis — topics that would benefit engineering students today. And the examples, while clear, are almost exclusively deterministic; there is no discussion of error propagation or uncertainty quantification using differentials, though the “approximations” section touches on it lightly. Conclusion: The Unfinished Journey Chapter 10 of Differential and Integral Calculus by Feliciano and Uy is more than a collection of problems on tangents, optimization, and related rates. It is a rite of passage — a demanding, patient, and ultimately rewarding bridge from the rules of differentiation to the art of applying them. Its legacy is visible in every Filipino engineer who can quickly sketch a curve, size a container for maximum volume, or compute how fast a shadow lengthens as a streetlight walks away. One problem might involve a lighthouse rotating its
Chapter 10, typically titled or “Further Applications of the Derivative” (depending on the edition), is where the abstract machinery of limits, slopes, and derivatives transforms into a toolkit for solving real-world problems. This feature explores the chapter’s structure, its signature problems, the pedagogical philosophy behind it, and why it continues to challenge and inspire students today. The Bridge from Theory to Practice By the time a student reaches Chapter 10, they have survived the foundational gauntlet: limits (Chapter 1), continuity (Chapter 2), derivatives of algebraic functions (Chapters 3–5), trigonometric, logarithmic, and exponential functions (Chapters 6–8), and implicit differentiation (Chapter 9). They can compute $dy/dx$ in their sleep. But Chapter 10 asks a disarming question: Now that you can differentiate anything, what is it good for?
Yet the chapter does not coddle. The difficulty ramps up sharply. By the last set of problems, students face (e.g., $x^3 + y^3 = 6xy$, the folium of Descartes) and must find tangents, normals, and extreme values without explicitly solving for $y$. This prepares them for higher-level courses like differential equations and multivariable calculus. A Cultural Touchstone In the Philippines, Feliciano and Uy is more than a textbook — it’s a cultural artifact. Chapter 10, in particular, is where study groups form, where tutors earn their keep, and where many students first encounter the satisfying click of a difficult word problem solved correctly. The shared trauma of “the ladder problem” or “the box problem” creates camaraderie.