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.
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? The section is particularly feared
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. Feliciano and Uy were writing for students who
Another strength is the chapter’s . Early exercises are straightforward: find the slope of the tangent to $y = x^3 - 3x$ at $x=2$. By the end of the problem set, students face multi-step optimization puzzles involving costs, revenues, and geometric constraints that mimic real engineering design challenges. The Infamous “Feliciano and Uy” Problem Sets Ask any Filipino engineer over 40 about Chapter 10, and they will likely grimace with a fond nostalgia. The unsolved exercises at the back of each subsection are legendary — not because they are impossible, but because they require translation from English to mathematics. Consider this classic optimization problem (paraphrased from memory of the 1980s edition): “A rectangular sheet of tin 12 inches by 8 inches has four equal squares cut from each corner. The flaps are then folded up to form an open box. Find the size of the square to be cut out so that the volume of the box is maximum.” The solution requires defining $x$ as the side of the square, expressing volume $V(x) = (12-2x)(8-2x)x$, differentiating, setting $V'(x)=0$, and checking the second derivative. Simple enough — but Feliciano and Uy often add a twist: “If the tin costs PhP 0.50 per square inch and the box is to be sold for PhP 15.00, is it profitable?” Suddenly, it’s not just calculus; it’s economics. Chapter 10, typically titled or “Further Applications of
As Feliciano and Uy themselves might say, at the end of the chapter’s answer key (printed in the back, always with just the final answers, no full solutions): “Now proceed to Chapter 11: The Definite Integral.” Because calculus, like learning, never truly ends — it only accumulates. Page numbers, exact problem statements, and subsection titles vary by edition (e.g., the 1978 SIBS Publishing edition vs. the 1990s reprints). However, the structure and spirit of Chapter 10 have remained remarkably consistent — a testament to the timeless pedagogy of Feliciano and Uy.
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.
Moreover, the chapter introduces — problem-solving strategies. For optimization, students are taught: 1) Draw a diagram. 2) Identify the quantity to be optimized. 3) Express it in terms of one variable. 4) Differentiate. 5) Test critical points. This recipe-like clarity is comforting to students who find pure mathematics intimidating.