Problem 9 - Thomas Calculus in SI Units

Question

Rewrite the expressions in terms of exponentials and simplify the results as much as you can. $$(\sinh x+\cosh x)^{4}$$

Step-by-Step Solution

Answer

\((\sinh x + \cosh x)^{4} = e^{4x}\)

Step 1: Rewrite Hyperbolic Functions

Express the hyperbolic sine and cosine in terms of exponentials:\[ \sinh x = \frac{e^x - e^{-x}}{2}, \quad \cosh x = \frac{e^x + e^{-x}}{2} \]

Step 2: Combine Hyperbolic Functions

Substitute the exponential expressions for \(\sinh x\) and \(\cosh x\) into the original expression:\[ (\sinh x + \cosh x) = \left(\frac{e^x - e^{-x}}{2} + \frac{e^x + e^{-x}}{2}\right) = e^x \]

Step 3: Simplify the Expression

Now raise the simplified base \(e^x\) to the fourth power:\[ (e^x)^{4} = e^{4x} \]

Key Concepts

Exponential Functions

Exponential functions are mathematical expressions where a constant base is raised to a variable exponent. These functions frequently appear in various areas of mathematics including hyperbolic functions, which are often expressed using exponential functions for simplification. When dealing with hyperbolic identities, such as \[ \sinh x = \frac{e^x - e^{-x}}{2} \quad \text{and} \quad \cosh x = \frac{e^x + e^{-x}}{2} \]we see that hyperbolic sine and cosine can be rewritten in terms of exponentials. This makes them easy to manipulate algebraically, as exponentials have simpler properties for integration and differentiation. In the context of the original exercise, noticing these exponential forms helps in transforming hyperbolic functions to exponential functions. This step is crucial as it aids in subsequent algebraic manipulation and simplifications of expressions.

Simplification Techniques

Simplification is the process of transforming an expression into a more manageable or easily interpretable form. In algebra, this often involves the use of identities or properties to combine like terms, cancel out terms, or reduce expressions to their simplest form. For instance, when simplifying the expression \[ \sinh x + \cosh x = \frac{(e^x - e^{-x}) + (e^x + e^{-x})}{2} \]we notice that the subtraction and addition within the numerator result in \[ \frac{2e^x}{2} \]thereby simplifying the expression directly to \[ e^x \]This integral simplification step reduces the complexity of further algebraic manipulations and computations, demonstrating how using exponential expressions can lead to quick and straightforward simplifications.

Algebraic Manipulation

Algebraic manipulation involves performing operations such as addition, subtraction, multiplication, division, and exponentiation according to specific rules to rearrange or simplify expressions. This skill is fundamental in solving equations and understanding patterns within mathematical expressions.In the given problem, once the hyperbolic expression was rewritten as \[ e^x \]the next task was to manipulate it further by raising it to the fourth power. This was straightforward, following the rule \[ (a^m)^n = a^{m \times n} \]yielding \[ (e^x)^4 = e^{4x} \]This manipulation highlights how understanding the rules of exponents can simplify complex expressions efficiently. Each step is crucial in mathematics to ensure clarity and correctness in arriving at a final, simplified form.