# 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.

$2+2=4$

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

$1/2=0.5$

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.

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

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

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

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

$E = mc^{2}$

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.

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

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

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

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

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

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

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

$\int_{3}^{21}\frac{1}{x}dx = \log(7)$
$e^{j\theta} = \cos(\theta) + j\sin(\theta)$ 