# 2D Parametric plots in pgf

I am trying to plot a parametric parabola given by x(t)=125cos(30)t and y(t)=3+125sin(30)t-16t^2

Here is my code

\begin{center}
\begin{tikzpicture}
\begin{axis}
({125*t*cos(deg(30)))},
{3+125*t*sin(deg(30))-16*t^2});
\end{axis}
\end{tikzpicture}
\end{center}


This is what i get:

And this is what I'm after

• Your code has an x^2 in it. Is it supposed to be t^2? – Willie Wong Jul 17 '16 at 2:28
• I was about to freak out, but i changed it and it didnt help – Tony Mau Jul 17 '16 at 2:53
• What did you get as an output? – Willie Wong Jul 17 '16 at 2:58
• I just edited my original post. unfortunaly i dont know how to generate the graph without converting the whole page to a .png – Tony Mau Jul 17 '16 at 3:05

1. By issuing domain=0:4 you are telling TikZ to plot between t = 0 and t = 4. It appears from your desired output you want to plot between approximately x = 0 and x=4.
2. By issuing deg(30) you are not plotting cosine and sine of 30 degrees; instead you are plotting cosine and sine of 30 radians. (The deg function converges from radians to degrees; TikZ's trigonometry functions assume its arguments are in degrees.)
To get the plot you want, you probably want to remove the calls to deg (since I am pretty sure you don't want something bizarre like 30 radians). And you should also change your domain to something like 0:0.05 which would give upper and lower bounds for x to be approximately 0 to 5.
• No: in TikZ when you type sin(x) it is expected that x is the angle in degrees. If you want to use radian values, you have to first convert the radian value r to degrees by issuing deg(r). So deg(2*pi) is equal to 360. (In other words, deg is a function that takes input a radian angle measure and outputs the equivalent degree measure.) – Willie Wong Jul 17 '16 at 3:47