Inverse Functions and Angle Formulas
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Questions and Answers

What are the two general steps to find the inverse function of a given function?

First, find x in terms of y, then switch x and y.

Why does the function 𝑦 = 𝑥^2 not have an inverse?

Because for y = 4, there are two values of x (2 and -2) that satisfy the equation, leading to ambiguity.

What is the 'Horizontal Line Test' and why is it significant?

The Horizontal Line Test checks if a horizontal line intersects a graph at more than one point, indicating the function has no inverse.

Under what conditions does a function have an inverse?

<p>A function has an inverse if it is either strictly increasing or strictly decreasing.</p> Signup and view all the answers

If given y = f(x), how can you determine if f has an inverse?

<p>You can determine if f has an inverse by checking if the equation f(x1) = f(x2) implies x1 = x2.</p> Signup and view all the answers

What is the relationship between the uniqueness of outputs and the existence of an inverse function?

<p>A function must have unique outputs for every input to possess an inverse function.</p> Signup and view all the answers

How can you find the inverse of the function y = x^3 - 2?

<p>First, express x in terms of y as x = (y + 2)^(1/3), then switch to get y = (x + 2)^(1/3).</p> Signup and view all the answers

What happens if two different x-values produce the same output in a function?

<p>If two different x-values yield the same output, the function does not have an inverse.</p> Signup and view all the answers

What is the final expression for cos(𝛼 − 𝛽) derived from the equation presented?

<p>cos(𝛼 − 𝛽) = cos 𝛼 cos 𝛽 + sin 𝛼 sin 𝛽.</p> Signup and view all the answers

How does the expansion of [cos(𝛼 − 𝛽) − 1]² relate to the identity of cosine?

<p>It expands to 2 - 2 cos(𝛼 − 𝛽), which simplifies using the Pythagorean identity.</p> Signup and view all the answers

What formula is derived for the sum of angles from the difference of angles formula?

<p>cos(𝛼 + 𝛽) = cos 𝛼 cos 𝛽 − sin 𝛼 sin 𝛽.</p> Signup and view all the answers

What leads to the simplification of the right-hand side during the expansion?

<p>Combining cos² and sin² terms with Pythagorean identities results in a simplified expression.</p> Signup and view all the answers

Identify the role of the negative sign in the angle sum formula proof.

<p>The negative sign indicates the sine function of a negative angle, defining its value as a negative.</p> Signup and view all the answers

What do the terms 2 − 2 cos(𝛼 − 𝛽) equate to when manipulated?

<p>They equate to 2 − 2(cos 𝛼 cos 𝛽 + sin 𝛼 sin 𝛽).</p> Signup and view all the answers

What basic identity is applied during the proof of the sum of angles formula?

<p>The basic identity applied is cos²θ + sin²θ = 1.</p> Signup and view all the answers

How is the term sin(−𝛽) treated in the context of the angle addition formula?

<p>It is treated as −sin(𝛽) due to the properties of the sine function.</p> Signup and view all the answers

Explain the difference between sin^(-1)x and arcsin(x).

<p>sin^(-1)x can refer to the inverse sine function or to csc(x), while arcsin(x) specifically denotes the inverse sine function with restricted domains.</p> Signup and view all the answers

Why are the functions arcsin, arccos, arctan, and arccot not pure inverses of their respective sine, cosine, tangent, and cotangent functions?

<p>They are not pure inverses as they only apply to outputs within restricted domains, which ensures unique values.</p> Signup and view all the answers

Compute arcsin(sin(7)). What is the reasoning behind your answer?

<p>arcsin(sin(7)) = 7 - 2π because 7 is outside the acceptable range of the arcsin function.</p> Signup and view all the answers

What happens when you attempt to compute sin(arcsin(7))?

<p>sin(arcsin(7)) = DNE (Does Not Exist) because 7 exceeds the range of the sine function (-1 to 1).</p> Signup and view all the answers

Define the range of values of the arcsin function.

<p>The range of arcsin is restricted to $[-π/2, π/2]$.</p> Signup and view all the answers

When does the equation sin(b) = sin(7) hold true for b within the range of arcsin?

<p>The equation holds true when b = 7 - 2π, since this value lies within the arcsin range.</p> Signup and view all the answers

Illustrate how to determine if an angle is valid for an inverse trigonometric function.

<p>An angle is valid for an inverse trigonometric function if it falls within the function's specific range.</p> Signup and view all the answers

For the function csc(x), what is its relationship with sin(x)?

<p>csc(x) is the reciprocal of sin(x), defined as 1/sin(x).</p> Signup and view all the answers

What type of discontinuity does the function $f(x) = \frac{\tan(x)}{\sin(x)}$ exhibit at $x = 0$?

<p>It has a removable discontinuity at $x = 0$.</p> Signup and view all the answers

State the Intermediate Value Theorem in simple terms.

<p>If $f$ is a continuous function on the interval $[a, b]$, then it takes every value between $f(a)$ and $f(b)$.</p> Signup and view all the answers

Why must you 'hit every point in between' when applying the Intermediate Value Theorem?

<p>Because a continuous function cannot be broken, meaning you cannot lift your pencil while drawing it.</p> Signup and view all the answers

Show that the function $f(x) = x - \cos(x)$ has a zero in the interval $[0, \frac{\pi}{2}]$. How are the values at the endpoints significant?

<p>At $f(0) = -1$ and $f(\frac{\pi}{2}) = \frac{\pi}{2}$, by the IVT, since $-1 &lt; 0 &lt; \frac{\pi}{2}$, there is a $c$ where $f(c) = 0$.</p> Signup and view all the answers

Explain how the Intermediate Value Theorem proves the existence of a unique $c > 0$ such that $c^n = \zeta$ for $\zeta > 0$.

<p>The IVT ensures that for every positive $eta$ between $0$ and $\zeta$, there is a corresponding $c$ that satisfies $c^n = \beta$.</p> Signup and view all the answers

Discuss the significance of continuity in relation to the function $f(x) = x - \cos(x)$.

<p>$f(x)$ is continuous since both $x$ and $\cos(x)$ are continuous functions, enabling the application of the IVT.</p> Signup and view all the answers

What conclusion can be drawn from the behavior of the function $f(x) = \frac{\tan(x)}{\sin(x)}$ near $x = 0$?

<p>The limits as $x$ approaches 0 highlight the removable discontinuity and indicate the limit is 1.</p> Signup and view all the answers

Why is the Intermediate Value Theorem considered 'incredibly useful'?

<p>It allows us to show that functions attain certain values over an interval, which is fundamental in analysis.</p> Signup and view all the answers

What is the general formula for a tangent line at point (a, f(a))?

<p>The general formula is given by $y - y_0 = k(x - x_0)$.</p> Signup and view all the answers

How does the process of finding the slope of a tangent line begin?

<p>It begins by selecting another point, x, and calculating the slope of the line through (a, f(a)) and (x, f(x)).</p> Signup and view all the answers

In the context of derivatives, what is the purpose of moving x closer to a?

<p>The purpose is to obtain the slopes of the tangent lines that converge towards the slope at x = a.</p> Signup and view all the answers

What does the difference quotient represent in the process of finding a derivative?

<p>The difference quotient represents the slope of the secant line, calculated as $\frac{f(x) - f(a)}{x - a}$.</p> Signup and view all the answers

What is meant by the notation $\lim_{x \to a}$ in the context of derivatives?

<p>It denotes taking the limit of the difference quotient as x approaches the point a.</p> Signup and view all the answers

What is the significance of the function f(x) being defined at point a?

<p>It ensures that the tangent line can be accurately evaluated at that specific point.</p> Signup and view all the answers

How do we mathematically express the derivative of f(x) at a using limits?

<p>The derivative is expressed as $f'(a) = \lim_{x \to a} \frac{f(x) - f(a)}{x - a}$.</p> Signup and view all the answers

What does it mean for slopes of tangent lines to get 'closer and closer' to a specific value?

<p>It implies that as x approaches a, the calculated slopes converge to the exact slope of the tangent line at that point.</p> Signup and view all the answers

Using the definition of the derivative, show how you can calculate the derivative of 𝑓(𝑥) = 𝑐 where 𝑐 is a constant.

<p>The derivative is 𝑓 ′(𝑥) = lim (𝑐 - 𝑐)/ℎ as ℎ approaches 0, which simplifies to 0.</p> Signup and view all the answers

Explain why the derivative of 𝑓(𝑥) = 𝑥 is equal to 1 for all x.

<p>The derivative is calculated as 𝑓 ′(𝑥) = lim (ℎ)/(ℎ) as ℎ approaches 0, resulting in 1.</p> Signup and view all the answers

Derive 𝑓 ′(𝑎) for the function 𝑓(𝑎) = cos(𝑎) using the definition of the derivative.

<p>𝑓 ′(𝑎) = lim (cos(𝑎 + ℎ) - cos(𝑎))/ℎ as ℎ approaches 0 = -sin(𝑎).</p> Signup and view all the answers

Provide a brief explanation of why the limit process is essential in finding the derivative of functions.

<p>The limit process helps determine the instantaneous rate of change, which the derivative represents, by considering values arbitrarily close to a point.</p> Signup and view all the answers

What is the significance of the negative sign in the derivative of the cosine function?

<p>The negative sign indicates that the slope of the cosine function is decreasing, which aligns with its behavior as it transitions from positive to negative values.</p> Signup and view all the answers

Flashcards

Inverse function

A function that reverses the effect of another function. If f(x) = y, then the inverse function, denoted by f⁻¹(y) = x.

Finding the inverse function (Step 1)

Express the input variable (x) in terms of the output variable (y).

Finding the inverse function (Step 2)

Swap the input and output variables (x and y).

Horizontal Line Test

A test to determine if a function has an inverse. A function has an inverse if and only if no horizontal line intersects its graph more than once.

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Strictly increasing function

A function where f(x1) < f(x2) for all x1 < x2 in its domain.

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Strictly decreasing function

A function where f(x1) > f(x2) for all x1 < x2 in its domain.

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Inverse function existence

A function has an inverse if and only if it is either strictly increasing or strictly decreasing.

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One-to-one function

A function where each input (x-value) corresponds to a unique output (y-value).

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Cosine Difference Formula

The formula that expresses the cosine of the difference of two angles (α - β) in terms of the cosines and sines of the individual angles.

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Expanding the left-hand side

Applying the algebraic distributive property to simplify the term [cos (α - β) - 1]² + sin²(α - β) by multiplying and combining like terms.

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Expanding the right-hand side

Applying the algebraic distributive property to simplify the term (cos α - cos β)² + (sin α - sin β)² by multiplying and combining like terms.

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Combining left and right sides

Equating the simplified expressions of the left-hand side and right-hand side to arrive at a simplified equation.

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Cosine Sum Formula

The formula that expresses the cosine of the sum of two angles (α + β) in terms of the cosines and sines of the individual angles.

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Proving the Sum Formula

Deriving the cosine sum formula by using the cosine difference formula and substituting (-β) for β.

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Deriving the Sum Formula

The process of using previously proven identities and algebraic manipulation to derive a new formula.

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Trigonometric Identity

An equation that holds true for all possible values of the variables involved, typically involving trigonometric functions.

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Removable Discontinuity

A type of discontinuity where the function can be made continuous by redefining one point.

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Intermediate Value Theorem (IVT)

If a continuous function on a closed interval takes on two values, it must also take on all values in between.

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Continuous Function

A function where the graph can be drawn without lifting the pen from the paper.

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Closed Interval

An interval that includes both its endpoints.

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Bounded Interval

An interval that has finite endpoints.

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Zero of a Function

A value of x where the function equals zero.

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Unique Number

The only one of its kind, there can't be another.

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nth root

The number that, when multiplied by itself n times, equals the given number.

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arcsin

The inverse function of sine (sin) when the domain of sine is restricted to -π/2 ≤ x ≤ π/2.

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arccos

The inverse function of cosine (cos) when the domain of cosine is restricted to 0 ≤ x ≤ π.

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arctan

The inverse function of tangent (tan) when the domain of tangent is restricted to -π/2 < x < π/2.

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arccot

The inverse function of cotangent (cot) when the domain of cotangent is restricted to 0 < x < π.

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Why can't we always cancel arcsin and sin?

The arcsin and sin functions are not inverse functions in all cases. They are only inverses when the input of arcsin is within the restricted domain of sine (-π/2 ≤ x ≤ π/2).

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What is the range of arcsin?

The range of arcsin is -π/2 ≤ y ≤ π/2. It's the same as the restricted domain of sine.

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What is the range of arccos?

The range of arccos is 0 ≤ y ≤ π. It's the same as the restricted domain of cosine.

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What is the range of arctan?

The range of arctan is -π/2 < y < π/2. It's the same as the restricted domain of tangent.

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Derivative of cos(x)

The derivative of the cosine function, represented by (cos(x))' or d/dx(cos(x)), is equal to -sin(x).

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Derivative of x

The derivative of the function f(x) = x is 1. This means the slope of the tangent line to the graph of y = x is always 1.

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Derivative of a constant

The derivative of a constant function f(x) = c is 0. This indicates that the slope of the tangent line to the graph of y = c is always zero, meaning it's a horizontal line.

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Finding the derivative

The process of determining the derivative of a function involves calculating the instantaneous rate of change of the function at a particular point. This involves finding the limit of the difference quotient as the change in x approaches zero.

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Difference quotient

The expression representing the average rate of change of a function f(x) over an interval h is called the difference quotient. It is defined as [f(x + h) - f(x)] / h.

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Tangent line

A line that touches a curve at a single point and has the same slope as the curve at that point.

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Slope of a tangent line

The rate of change of a curve at a specific point, represented by the slope of the tangent line at that point.

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Limit in the difference quotient

Taking the limit of the difference quotient as the second point approaches the first point to find the exact slope of the tangent line.

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Derivative

The instantaneous rate of change of a function at a point, obtained by finding the limit of the difference quotient as the second point approaches the first point.

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What is the derivative used for?

The derivative is used to find the instantaneous rate of change of a function at a given point. It can also be used to find the maximum or minimum points of a function.

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Function 𝑓(𝑥)

A function that assigns a unique output value for every input value.

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Point (𝑎, 𝑓(𝑎))

A point on the graph of the function 𝑓(𝑥) where the input value is 𝑎 and the output value is 𝑓(𝑎).

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Study Notes

Course Information

  • Course: Calculus I
  • Instructor: Han Li
  • Office: Exley 639
  • Phone: 860-685-3221
  • Email: [email protected]

Course Syllabus

  • Reference and Lecture Notes: The primary resource is an OpenStax Calculus I textbook. The instructor will also develop their own lecture notes that may cover additional material.
  • Course Description: The course covers limits, derivatives, integrals, and applications of calculus, including sequences and series, with a focus on exponential, logarithmic, trigonometric, and inverse trigonometric functions.
  • Grading Policy:
    • Homework: 9 sets, each worth 20 points. Drop the 3 lowest grades. Total homework grade is out of 120.
    • Midterm Exam: Monday, November 4, during class time. Worth 80 points.
    • Final Exam: Wednesday, December 11, 9 AM to noon. Worth 100 points.
    • Attendance: Missing up to two lectures does not affect the grade. Each lecture missed beyond the third one and not supported by a class dean results in 5-point deduction.
    • Course Score Calculation: The final course score is the higher of two options (S1 or S2).
      • S₁ = H + M + F − A
      • S₂ = 3F
      • Where H is the total homework grade, M is the midterm score, F is the final exam score, and A is an attendance adjustment score.
      • Course scores are out of a total of 300.
    • Final Grade Determination: Final grades are based on the course score and class ranking. Specific score ranges (e.g. ≥ 270/300) and percentile brackets define grade cutoffs (e.g., top 20% = A).

Policies

  • Makeup Exams: Makeup exams will only be considered for significant life events with supporting documentation from the class dean.
  • Homework Submission: Homework must be submitted through Moodle as a single PDF file by the deadline. Late submissions are not accepted.
  • Course Attendance: Late arrivals, and/or early dismissals are handled separately.

Additional Information

  • Accommodations: Wesleyan University provides accommodations for students with disabilities, so students should contact Accessibility Services.
  • Religious/Spiritual Observances: The university supports students' religious and spiritual observances.
  • Title IX Resources: The university offers resources related to issues of gender-based violence, discrimination and harassment.
  • Honor Code: Students are fully responsible for adhering to the Wesleyan Honor Code.

Tables and Figures (Content)

  • Course Content Outline: A summary of the course material outline (Topics like Trigonometric Functions, Limits, The Derivative, Applications)

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Calculus I Course Syllabus PDF

Description

This quiz covers essential concepts related to inverse functions, including the conditions for existence and methods to find them. It also explores the trigonometric identities related to the sum and difference of angles, particularly focusing on cosine. Perfect for students studying advanced algebra and trigonometry.

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