Melody

just enter it on the home page calc as

[2nd] atan (2/18)

the radian / degrees button is in the bottom left corner.

If you want the remainder when 50 is divided by 6 youcan put it into the web2.0calc like this.  

mod(50,6)

$${\mathtt{50}} \,{mod}\, {\mathtt{6}} = {\mathtt{2}}$$

Thanks Chris,

I didn't lok at them very hard but the first one looked like it might be quite good.

$$$I always start with $\\\\
\begin{array}{rll}
gradient&=&gradient\\\\
\frac{y-y_1}{x-x_1}&=&\frac{y_2-y_1}{x_2-x_1}\\
\end{array}$$

Take a look at this. 

Here are 2 resources that you might find very good.

3/11=9/33

so

9:12

3:4

When you are adding an subtracting with letters, you can think of the letters as things.

2 rabbits+3 rabbits = 5 rabbits

so

2r+3r=5r

OR

$$\begin{array}{rll}
g(x)&=&2^{-x}\\
log_2[g(x)]&=&log_2\;2^{-x}\\
x&=&-log_2[g(x)]




\end{array}$$

Use the calc on the home page.