Problem 1 - Thomas Calculus

Question

In Exercises \(1-12,\) find \(d y / d x\) $$ y=-10 x+3 \cos x $$

Step-by-Step Solution

Answer

\(\frac{dy}{dx} = -10 - 3\sin x\)

Step 1: Differentiate the Linear Term

We start by differentiating the first term of the function, \(-10x\). The derivative of a linear term \(-10x\) with respect to \(x\) is simply the coefficient of \(x\). Thus, the derivative is \(-10\).

Step 2: Differentiate the Trigonometric Term

Now, we differentiate the second term, \(3\cos x\). The derivative of \(\cos x\) is \(-\sin x\). Thus, the derivative of \(3\cos x\) is \(3(-\sin x) = -3\sin x\).

Step 3: Combine the Derivatives

Finally, we combine the derivatives of each term that we found in the previous steps. Therefore, the overall derivative is the sum of the derivatives of the terms: \(\frac{dy}{dx} = -10 - 3\sin x\).

Key Concepts

The Basics of Derivatives

Understanding derivatives is crucial in calculus. They represent the rate at which a function changes as its input changes. If you imagine driving a car, the derivative of your distance over time is your speed, showing how fast you're going. In mathematical terms, the derivative of a function \(f(x)\) with respect to \(x\) is denoted by \(f'(x)\) or \(\frac{df}{dx}\). This notation reflects the "change in \(f\) with respect to change in \(x\)."For linear functions like \(-10x\), the derivative is simply the coefficient of \(x\). This is because the slope, which the derivative represents, is constant. For more complex or non-linear functions, however, finding the derivative involves more intricate rules and methods.

Introduction to Trigonometric Derivatives

Trigonometric derivatives are an essential part of calculus, particularly when dealing with functions that include trigonometric components such as \(\sin x\), \(\cos x\), and \(\tan x\). Understanding these derivatives helps us analyze how trigonometric functions change over different inputs. Here are a few key derivatives:

• The derivative of \(\sin x\) is \(\cos x\).
• The derivative of \(\cos x\) is \(-\sin x\).
• The derivative of \(\tan x\) is \(\sec^2 x\).

In our original problem, we used the derivative of \(\cos x\), which is \(-\sin x\). So, when differentiating \(3\cos x\), we multiply the constant \(3\) by \(-\sin x\), resulting in the term \(-3\sin x\). This process demonstrates how the derivative behaves similarly to a scaling factor for the function.

A Dive into Calculus and its Applications

Calculus is fundamentally about change and accumulation. Derivatives are the tool that calculus provides for examining the first part of this process—understanding change. They allow us to determine how a function behaves at any point, offering insights into trends, maxima, minima, and more. In practical terms:

• Physics uses calculus to describe motion through the derivatives as velocity and acceleration.
• Economics uses them to find optimal production levels.
• Biology uses them for modeling population changes.

In solving calculus problems, it's important to apply differentiation rules methodically, as seen with our example. Recognizing constant multiples and trigonometric identities, like we did, is part of becoming proficient in calculus. It makes solving complex equations more manageable and provides essential insights, whether for scientific research or everyday calculations.