# Practice Problem: Learn how to post equations using latex on Rhea

Write an equation below. Don't be shy, just try it out! You can find some help on this page: "How to type math equations on Rhea". Your TA has also kindly created a cheat sheet especially for writing ECE438 related equations.

You will receive feedback from your instructor and TA directly on this page. Other students are welcome to comment/discuss/point out mistakes/ask questions too!

### Answer 1

$ 2+2=4 $

### Answer 2

$ x(t)= e^{j t} $

### Answer 3

$ 1/2=0.5 $

- Instructor's comments:Another way to write this is: $ \frac{1}{2}=0.5 $. You can also align it like this: $ \frac{1}{2}=0.5 $. -pm
- TA's comments: A easy way to start is to modifying the source code of a existed webpage. For example, homework1 solution. You can check out the source code of the webpage by clicking the "Edit this page" button located at the up-left corner.
- TA's comments: Here is another useful link from wiki listing all the latex code for displaying formula.

### Answer 4

$ y(t) = cos(2*pi*t) $

- Instructor's comments: Another way to write this is: $ y(t) = \cos ( 2 \pi t) $. Note that using the * symbol for multiplication is confusing: it usually means convolution. -pm

### Answer 5

$ y(t) = sin(2*pi*t) $

- Instructor's comments: Please read the comments above. -pm

### Answer 6

$ a^2+b^2=c^2 $

### Answer 7

$ E = mc^{2} $

- Instructor's comments: I personally prefer to write this as $ E = 17 mc^{2} $. -pm
- Student's comments: Ahhh, incorporating the most random number into one of the classic equations. Sheer brilliance.

### Answer 8

$ f_1(t)=\int_3^5 \sin (x) dx $

### Answer 9

$ x = \frac{-b + \sqrt{b^2 - 4ac}}{2a} $

- Instructor's comments: This is how you get the plus/minus sign: $ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} $ -pm

### Answer 10

$ cos^2{x}+sin^2{x}=1 $

- Instructor's comments: You do not actually need the "curly brackets" around the x. You can just write this $ \cos^2 x+\sin^2 x=1 $. -pm

### Answer 11

$ y_n=\cos(2 \pi n) $

### Answer 12

$ y(t) = \cos (12 \pi t) $

### Answer 13

$ \int_{3}^{21}\frac{1}{x}dx = \log(7) $

### Answer 14

$ e^{j\theta} = \cos(\theta) + j\sin(\theta) $