Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 3h 16m
- 11. Integrals of Inverse, Exponential, & Logarithmic Functions2h 34m
- 12. Techniques of Integration7h 39m
- 13. Intro to Differential Equations2h 55m
3. Techniques of Differentiation
The Chain Rule
Problem 3.6.43
Textbook Question
In Exercises 41–58, find dy/dt.
y = (1 + cos(2t))⁻⁴

1
Identify the function y = (1 + cos(2t))^(-4) and recognize that you need to find the derivative dy/dt.
Apply the chain rule for differentiation. The chain rule states that if you have a composite function y = f(g(t)), then dy/dt = f'(g(t)) * g'(t).
Differentiate the outer function f(u) = u^(-4) with respect to u, which gives f'(u) = -4u^(-5).
Substitute u = 1 + cos(2t) into the derivative of the outer function, resulting in -4(1 + cos(2t))^(-5).
Differentiate the inner function g(t) = 1 + cos(2t) with respect to t. The derivative of cos(2t) is -2sin(2t), so g'(t) = -2sin(2t). Multiply this result by the derivative of the outer function to get dy/dt = -4(1 + cos(2t))^(-5) * (-2sin(2t)).

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chain Rule
The chain rule is a fundamental technique in calculus used to differentiate composite functions. It states that if a function y = f(g(t)) is composed of two functions, then its derivative dy/dt is f'(g(t)) * g'(t). This rule is essential for finding the derivative of y = (1 + cos(2t))⁻⁴, as it involves differentiating the outer function and the inner function separately.
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Trigonometric Derivatives
Understanding the derivatives of trigonometric functions is crucial for solving this problem. The derivative of cos(t) is -sin(t), and when dealing with cos(2t), the chain rule must be applied, resulting in the derivative -2sin(2t). This knowledge is necessary to differentiate the inner function of the composite function y = (1 + cos(2t))⁻⁴.
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Power Rule
The power rule is used to differentiate functions of the form y = x^n, where the derivative is n*x^(n-1). In this problem, the function y = (1 + cos(2t))⁻⁴ can be differentiated using the power rule, treating the entire expression inside the parentheses as a single variable. This rule helps in finding the derivative of the outer function in the composite expression.
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