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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 7, Problem 7.6.39

In Exercises 21–48, find the derivative of y with respect to the appropriate variable.
39. y=arctan√(x²-1) + arccsc(x), x>1

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Identify the function to differentiate: \(y = \arctan\left(\sqrt{x^{2} - 1}\right) + \arccsc(x)\), where \(x > 1\).
Recall the derivative formulas: For \(y = \arctan(u)\), \(\frac{dy}{dx} = \frac{1}{1 + u^{2}} \cdot \frac{du}{dx}\); for \(y = \arccsc(x)\), \(\frac{dy}{dx} = -\frac{1}{|x| \sqrt{x^{2} - 1}}\).
Differentiate the first term: Let \(u = \sqrt{x^{2} - 1} = (x^{2} - 1)^{1/2}\). Compute \(\frac{du}{dx}\) using the chain rule: \(\frac{du}{dx} = \frac{1}{2}(x^{2} - 1)^{-1/2} \cdot 2x = \frac{x}{\sqrt{x^{2} - 1}}\).
Apply the derivative formula for \(\arctan(u)\): \(\frac{d}{dx} \arctan\left(\sqrt{x^{2} - 1}\right) = \frac{1}{1 + (\sqrt{x^{2} - 1})^{2}} \cdot \frac{x}{\sqrt{x^{2} - 1}}\).
Differentiate the second term \(\arccsc(x)\) using its derivative formula: \(\frac{d}{dx} \arccsc(x) = -\frac{1}{|x| \sqrt{x^{2} - 1}}\). Since \(x > 1\), \(|x| = x\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Derivative of Inverse Trigonometric Functions

Inverse trigonometric functions like arctan and arccsc have specific derivative formulas. For example, the derivative of arctan(u) is u' / (1 + u²), and the derivative of arccsc(x) is -1 / (|x|√(x² - 1)). Knowing these formulas is essential to differentiate the given function correctly.
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Derivatives of Other Inverse Trigonometric Functions

Chain Rule

The chain rule is used to differentiate composite functions. When a function is composed of another function, such as arctan(√(x² - 1)), you first differentiate the outer function and then multiply by the derivative of the inner function. This rule is crucial for handling nested expressions.
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Intro to the Chain Rule

Simplification of Derivatives Involving Radicals and Algebraic Expressions

After applying differentiation rules, simplifying expressions involving radicals and algebraic terms like √(x² - 1) is important. This often involves rationalizing denominators or combining terms to present the derivative in a clear, simplified form.
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Integrals Involving Natural Logs: Substitution Example 8