How do I plot parabolas and other functions in MATLAB?

I'm trying to plot x2 +9y2 = 36 in MATLAB, but it just doesn't want to work, even if I split it up to 1/3sqrt(36 − x2) and −1/3sqrt(36 − x2)

I'm having trouble understanding what x=5:.5:5 means as well.

The second half of the question is y =3/2sin(2x +3) (I've already graphed this easily), and I need to find simultaneous solutions with the above function. Is ginput good enough for this?

Answer 1

[Youssef Khmou]

hi Joseph,

the expression means : variable=beginning:step:end , but 5:.5:5 is constant its 5 then . you can also plot the parabola just the way you did to the second equation :

   x=-10:0.1:10;
   y=sqrt((36-x.^2)/9);
   plot(x,y)

Warning: Imaginary parts of complex X and/or Y arguments ignored.