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 2h 22m
3. Techniques of Differentiation
Derivatives of Trig Functions
Problem 3.5.74a
Textbook Question
Find an equation of the line tangent to the following curves at the given value of x.
y = csc x; x = π/4

1
First, understand that the equation of a tangent line to a curve at a given point is y = mx + b, where m is the slope of the tangent line and b is the y-intercept.
To find the slope of the tangent line, calculate the derivative of the function y = csc(x). The derivative of csc(x) is -csc(x)cot(x).
Evaluate the derivative at the given point x = π/4. Substitute x = π/4 into the derivative -csc(x)cot(x) to find the slope m.
Next, find the y-coordinate of the point on the curve by substituting x = π/4 into the original function y = csc(x). This gives you the point (π/4, y).
Use the point-slope form of the equation of a line, y - y₁ = m(x - x₁), where (x₁, y₁) is the point on the curve and m is the slope, to write the equation of the tangent line.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Tangent Line
A tangent line to a curve at a given point is a straight line that touches the curve at that point without crossing it. The slope of the tangent line is equal to the derivative of the function at that point. This concept is crucial for finding the equation of the tangent line, as it provides the necessary slope to use in the point-slope form of a line.
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Derivative
The derivative of a function measures how the function's output value changes as its input value changes. It is a fundamental concept in calculus that provides the slope of the tangent line at any point on the curve. For the function y = csc x, the derivative can be calculated using differentiation rules, which will be needed to find the slope at x = π/4.
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Derivatives
Cosecant Function
The cosecant function, denoted as csc x, is the reciprocal of the sine function, defined as csc x = 1/sin x. Understanding the properties and behavior of the cosecant function is essential for evaluating the function and its derivative at specific points, such as x = π/4, which is necessary for determining the equation of the tangent line.
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