Home

#### The Six Pillars of Calculus

The Pillars: A Road Map
A picture is worth 1000 words

#### Trigonometry Review

The basic trig functions
Basic trig identities
The unit circle
Addition of angles, double and half angle formulas
The law of sines and the law of cosines
Graphs of Trig Functions

#### Exponential Functions

Exponentials with positive integer exponents
Fractional and negative powers
The function $f(x)=a^x$ and its graph
Exponential growth and decay

#### Logarithms and Inverse functions

Inverse Functions
How to find a formula for an inverse function
Logarithms as Inverse Exponentials
Inverse Trig Functions

#### Intro to Limits

Close is good enough
Definition
One-sided Limits
How can a limit fail to exist?
Infinite Limits and Vertical Asymptotes
Summary

#### Limit Laws and Computations

A summary of Limit Laws
Why do these laws work?
Two limit theorems
How to algebraically manipulate a 0/0?
Limits with fractions
Limits with Absolute Values
Limits involving Rationalization
Limits of Piece-wise Functions
The Squeeze Theorem

#### Continuity and the Intermediate Value Theorem

Definition of continuity
Continuity and piece-wise functions
Continuity properties
Types of discontinuities
The Intermediate Value Theorem
Examples of continuous functions

#### Limits at Infinity

Limits at infinity and horizontal asymptotes
Limits at infinity of rational functions
Which functions grow the fastest?
Vertical asymptotes (Redux)
Toolbox of graphs

#### Rates of Change

Tracking change
Average and instantaneous velocity
Instantaneous rate of change of any function
Finding tangent line equations
Definition of derivative

#### The Derivative Function

The derivative function
Sketching the graph of $f'$
Differentiability
Notation and higher-order derivatives

#### Basic Differentiation Rules

The Power Rule and other basic rules
The derivative of $e^x$

#### Product and Quotient Rules

The Product Rule
The Quotient Rule

#### Derivatives of Trig Functions

Two important Limits
Sine and Cosine
Tangent, Cotangent, Secant, and Cosecant
Summary

#### The Chain Rule

Two forms of the chain rule
Version 1
Version 2
Why does it work?
A hybrid chain rule

#### Implicit Differentiation

Introduction and Examples
Derivatives of Inverse Trigs via Implicit Differentiation
A Summary

#### Derivatives of Logs

Formulas and Examples
Logarithmic Differentiation

In Physics
In Economics
In Biology

#### Related Rates

Overview
How to tackle the problems

#### Linear Approximation and Differentials

Overview
Examples
An example with negative $dx$

#### Differentiation Review

Basic Building Blocks
Product and Quotient Rules
The Chain Rule
Combining Rules
Implicit Differentiation
Logarithmic Differentiation
Conclusions and Tidbits

#### Absolute and Local Extrema

Definitions
The Extreme Value Theorem
Fermat's Theorem
How-to

#### The Mean Value and other Theorems

Rolle's Theorems
The Mean Value Theorem
Finding $c$

#### $f$ vs. $f'$

Increasing/Decreasing Test and Critical Numbers
How-to
The First Derivative Test
Concavity, Points of Inflection, and the Second Derivative Test

#### Indeterminate Forms and L'Hospital's Rule

What does $\frac{0}{0}$ equal?
Indeterminate Differences
Indeterminate Powers
Three Versions of L'Hospital's Rule
Proofs

Strategies
Another Example

#### Newton's Method

The Idea of Newton's Method
An Example
Solving Transcendental Equations
When NM doesn't work

#### Anti-derivatives

Anti-derivatives and Physics
Some formulas
Anti-derivatives are not Integrals

#### The Area under a curve

The Area Problem and Examples
Riemann Sums Notation
Summary

#### Definite Integrals

Definition
Properties
What is integration good for?
More Examples

#### The Fundamental Theorem of Calculus

Three Different Quantities
The Whole as Sum of Partial Changes
The Indefinite Integral as Antiderivative
The FTC and the Chain Rule

### What does $\frac{0}{0}$ equal?

While we can't divide by zero, we can still meaningfully ask what happens to a ratio $\displaystyle{\frac{f(x)}{g(x)}}$ when both $f(x)$ and $g(x)$ go to zero. In fact, this sort of ratio appears every time we take a derivative: $$f'(x) = \lim_{h \to 0} \frac{f(x+h)-f(x)}{h}.$$ We can't just plug in $h=0$, since then both the numerator and denominator would be zero. It shouldn't be too surprising that derivatives can help us evaluate limits that look like $0/0$.

 L'Hospital's Rule: If $f(x)$ and $g(x)$ are continuous functions with $f(a)=g(a)=0$, then $$\lim_{x \to a}\, \frac{f(x)}{g(x)} = \lim_{x \to a}\, \frac{f'(x)}{g'(x)}.$$

There are other variations of this rule for evaluating limits that look like $\infty/\infty$, $0 \cdot \infty$, $\infty - \infty$, $1^\infty$ or $0^0$, or for taking limits as $x \to \pm \infty$. All these limits are called indeterminate forms. The complete statement of L'Hospital's rule and its proof is at the end of this learning module. For now we'll concentrate on learning how to apply the rule with some examples.

#### Indeterminate Quotients: $0/0$ or $\infty/\infty$

We start with indeterminate quotients, where either the numerator and denominator are both going to zero or are both blowing up.

 Example: Evaluate $\displaystyle{\lim_{x \to 0} \frac{x}{1-e^x}}$. Solution: First, note that both $f(x)=x$ and $g(x)=1-e^x$ are zero when $x=0$. So L'Hospital's rule applies. Then $$\lim_{x \to 0} \frac{x}{1-e^x} = \lim_{x\to 0} \frac{1}{-e^x} = \frac{1}{-e^0} = \frac{1}{-1} = -1.$$ Note that we are computing the ratio of $f'(x)=1$ and $g'(x)=-e^x$, not the derivative of $f/g$!

#### Indeterminate Products: $0 \cdot \infty$

Here we consider indeterminate products where one factor is going to zero and the other is blowing up.