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.obsidian/app.json vendored
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"vimMode": true, "vimMode": true,
"promptDelete": false, "promptDelete": false,
"pdfExportSettings": { "pdfExportSettings": {
"includeName": true,
"pageSize": "Letter", "pageSize": "Letter",
"landscape": false, "landscape": false,
"margin": "0", "margin": "0",

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# Trigonometric Identities
All of the following only apply when the denominator is not equal to zero.
$$ tan \theta = \frac{y}{x} $$
Because the following are inverses of their counterparts, you only need to remember the equivalents for $sin$, $cos$, and $tan$, then just find the inverse by taking $1/v$.
| Base Identity | Inverse Identity | Alternate Identities | Alternate Inverse Identities |
| ----------------------------- | ------------------------------ | --------------------------------------------- | --------------------------------------------------------------------- |
| $$ sin\theta = y $$ | $$ csc\theta = \frac{1}{y} $$ | | $$ csc\theta = \frac{1}{sin\theta} $$ |
| $$ cos\theta = x $$ | $$ sec \theta = \frac{1}{x} $$ | | $$ sec\theta = \frac{1}{cos\theta} $$ |
| $$ tan\theta = \frac{y}{x} $$ | $$ cot\theta = \frac{x}{y} $$ | $$ tan\theta = \frac{sin\theta}{cos\theta} $$ | $$ cot\theta = \frac{1}{tan\theta} = \frac{cos\theta}{sin{\theta}} $$ |
$$ cot \theta = \frac{x}{y} $$
$$ sec\theta = \frac{1}{cos\theta}$$
$$ csc\theta = \frac{1}{sin\theta}$$
# Pythagorean Identities
The Pythagorean identity expresses the Pythagorean theorem in terms of trigonometric functions. It's a basic relation between the sine and cosine functions.
$$ sin^2 \theta + cos^2 \theta = 1 $$
There are more forms that are useful, but they can be derived from the above formula:
$$ 1 + tan^2\theta = sec^2\theta $$
$$ cot^2 \theta + 1 = csc^2\theta $$
# Even and Odd Identities
- A function is even if $f(-x) = f(x)$.
- A function is odd if $f(-x) = -f(x)$
- Cosine and secant are **even**
- Sine, tangent, cosecant, and cotangent are **odd**.
## Examples
### Even and Odd Functions
> If $cot\theta = -\sqrt{3}$, what is $cot(-\theta)$?
$cot$ is an odd function, and so $cot(-\theta) = \sqrt{3}$
### Simplifying Using Identities
> Simplify $\frac{sin\theta}{cos\theta}$
1. The above equation can be split into two components
$$ \frac{sin\theta}{cos\theta} = \frac{sin\theta}{1} * \frac{1}{csc\theta} $$
2. Referring to the list of trig identities, we know that $\frac{1}{csc\theta}$ is equal to $sin\theta$.
$$ \frac{sin\theta}{1} * \frac{1}{csc\theta} = sin\theta * sin\theta $$
3. Simplifying further, we get:
$$ sin^2\theta $$

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| 2 | $180\degree - \theta$ | | 2 | $180\degree - \theta$ |
| 3 | $\theta - 180\degree$ | | 3 | $\theta - 180\degree$ |
| 4 | $360\degree - \theta$ | | 4 | $360\degree - \theta$ |
## Other Trigonometric Functions
All of the following only apply when the denominator is not equal to zero.
$$ tan \theta = \frac{y}{x} $$
Because the following are inverses of their counterparts, you only need to remember the equivalents for $sin$, $cos$, and $tan$, then just find the inverse by taking $1/v$.
$$ sec \theta = \frac{1}{x} $$
$$ csc = \frac{1}{y} $$
$$ cot \theta = \frac{x}{y} $$
## The Pythagorean Identity
The Pythagorean identity expresses the Pythagorean theorem in terms of trigonometric functions. It's a basic relation between the sine and cosine functions.
$$ sin^2 \theta + cos^2 \theta = 1 $$
# Definitions # Definitions
| Term | Description | | Term | Description |

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> 2. The following program fragments illustrate the logical operators. Show the output produced by each, assuming that `i`, `j`, and `k` are `int` variables.
a. `i = 10; j = 5;`
```c
printf("%d", !i < j);
// Expected output: `1`, because `!i` evaluates to 0, and 0 is less than 5, so that expression evaluates to true, or 1.
```
b. `i = 2; j = 1;`
```c
printf("%d", !!i + !j);
// Expected output: `1`, because !!2 evaluates to 1, and !j evaluates to 0
```
c. `i = 5; j = 0; k = -5;`
```c
printf("%d", i && j || k);
// Expected output: `1`, because i && j should evaluate to 0, but `0 || 1` should evalulate to true.
```
d. `i = 1; j = 2; k = 3;`
```c
printf("%d", i < j || k);
// Expected output: `1`
```
> 4. Write a single expression whose value is either `-1`, `0`, or `1` depending on whether `i` is less than, equal to, or greater than `j`, respectively.
```c
/*
If i < j, the output should be -1.
If i == j, the output should be zero
If i > j, the output should be 1.
*/
(i > j) - (i < j)
```
> 6. Is the following `if` statement legal?
```c
if (n == 1-10)
printf("n is between 1 and 10\n");
```
Yes the statement is *legal*, but it does not produce the intended effect. It would not produce an output when `n = 5`, because `1-10` evaluates to `-9`, and `-9 != 5`.
> 10. What output does the following program fragment produce? (Assume that `i` is an integer variable.)
```c
int i = 1;
switch (i % 3) {
case 0: printf("zero");
case 1: printf("one");
case 2: printf("two");
}
```
The program would print `onetwo` because each case is missing a `break` statement.
> 11. The following table shows the telephone area codes in the state of Georgia along with the largest city in each area:
| Area code | Major city |
| --------- | ---------- |
| 229 | Albany |
| 404 | Atlanta |
| 470 | Atlanta |
| 478 | Macon |
| 678 | Atlanta |
| 706 | Columbus |
| 762 | Columbus |
| 770 | Atlanta |
| 912 | Savannah |
> Write a switch statement whose controlling expression is the variable `area_code`. If the value of `area_code` is not in the table, the `switch` statement will print the corresponding city name. Otherwise, the `switch` statement will display the message `"Area code not recognized."` Use the techniques discussed in section 5.3 to make the `switch` as simple as possible.
```c
int area_code;
switch (area_code) {
case 404:
case 470:
case 678:
case 770:
printf("Atlanta");
break;
case 706:
case 762:
printf("Columbus");
break;
case 229:
printf("Albany");
break;
case 478:
printf("Macon");
break;
case 912:
printf("Savannah");
break;
default:
printf("Area code not recognized.");
break;
}
```

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> 2. The following program fragments illustrate the logical operators. Show the output produced by each, assuming that `i`, `j`, and `k` are `int` variables.
a. `i = 10; j = 5;`
```
printf("%d", !i < j);
```