Getting Points for Parabolas

• Download demo application - 50.8 KB
• Download source - 140.2 KB

Introduction 

Recently, I have been having a lot of algebra homework about graphing parabolas. It was a bit annoying doing the same process for all of my problems, so I decided to make a tool that will give me all the values I needed to graph:

• Vertex: Point where lines intersect
• Axis of symmetry: Line that will pass in the middle of the Parabola, in the X axis
• Y-intercept: Point where Y axis is intercepted, and X = 0
• Y-reflection: Another point to graph our Parabola

The Code

This code is really basic code, integers and decimals handling, so I will explain it a little bit.

decimal A = int.Parse(txt1.Text);
decimal B = int.Parse(txt2.Text);
decimal C = int.Parse(txt3.Text);
decimal X;
decimal Y;
decimal X_rf;
//Axis Of Sym Op                
decimal Axis_Sym = -1 * B / (2 * A);
axis_sym.Text = Axis_Sym.ToString();
X = Axis_Sym;
//Vertex Op
Y = A * (X * X) + B * X + C;
vertex.Text = X + " , " + Y;
//Y-Intercept Op
y_int.Text = X + " , " + C;
//Y_Ref Op              
X_rf = X + X;
y_ref.Text = X_rf + " , " + C; 

The code gets string values from 3 textboxes in the form, it converts the string value to decimal using Int.Parse(String). Once we have the decimal values (I used decimal in case the results of all the operations would come out as decimals). I'll describe the formulas to get the required points.

• Axis of Symmetry: Here we find X  = -(B) /  2 * A   
• Vertex: we need to get Y, so  Y = A(X)2 + B(X) + C so the vertex = (X, Y), a point in a coordinate plain.  
• Y-Intercept : A point where X = 0, and the line touches Y axis = (0, C) 
• Y-Reflection : Another point to graph our line = ( (X - X), C ) 

So that's it. We are ready to graph all the points, Soon I will add the code that actually graphs the points in a coordinate plane.

Points of Interest

This program was made by a 14 year old kid. This tool turned out to be really helpful.

History

• 26^th January, 2009: Initial post