How to Draw a Pentagon or Polygon by Using Function

Dear all,

I want to draw a pentagon and am using the code given below.

Vb is the height of the pentagon. X and Y are the limits of the coordinates in the given directions.

The problem is: when i plot i am getting the pentagon but lengths are not equal as shown in figure.

How can i get a regular pentagon?

Vb=250;
a=10;  %% size of pentagon
polyg = 5;

Nx=50; Ny=50; 
Mx=50; My=50;

x=linspace(-Mx/2,Mx/2,Nx);
y=linspace(-My/2,My/2,Ny);
[X,Y]=meshgrid(x,y);

f1 = (abs(X)<a*sind((polyg-2)*180/polyg));

f2 = (X*cotd(360/polyg)-a<Y)...
       .* (-X*cotd(360/polyg)-a<Y)...
       .* (-X*cotd(360/polyg)+a>Y);
   
fx = f1.*f2;

V0 = (1-fx)*Vb;

surf(X,Y,V0);

Answer 1

[Steven Lord]

Why not just use nsidedpoly?

P = nsidedpoly(5);
plot(P);
axis equal

[Özgür Alaydin]

I plot in 3d and also i needed as a function.

[Steven Lord]

So are you looking for a "column" with a pentagonal cross-section or are you looking for more of a dodecahedron?

P = nsidedpoly(5)

P = 
  polyshape with properties:

      Vertices: [5×2 double]
    NumRegions: 1
      NumHoles: 0

P.Vertices

ans = 5×2

-0.5878 -0.8090 -0.9511 0.3090 0 1.0000 0.9511 0.3090 0.5878 -0.8090

Use whatever mechanism you see fit to apply various affine transformations to these coordinates. Cleve Moler has written some tools that may be of interest: Grafix 2.0.

[Özgür Alaydin]

Not as i want because i will use integration after getting the coordinates of the pentagon.