Pythagoras Theorem Calculator | Visual Basic Examples

Understanding Pythagoras Theorem

The Pythagorean Theorem is a fundamental principle in geometry that relates the three sides of a right-angled triangle. It states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.

By referring to a right angled triangle ABC, where AC is the hypotenuse, the sides are connected by the formula:

AB² + BC² = AC²

Using this formula, you can calculate the third side if the length of any two sides are known. For example, if AB = 3 and BC = 4, then AC = 5.

AB

BC

AC

C

A

B

Interactive Pythagoras Calculator

Enter any two sides to calculate the third side of a right-angled triangle:

Pythagoras Calculator

Side AB (Adjacent):

Side BC (Opposite):

Hypotenuse AC:

Enter any two sides to calculate the third

Visual Basic Code Examples

VB6 Implementation

This VB6 code calculates the third side of a right-angled triangle when any two sides are provided:

Private Sub Command1_Click()
    Dim AB, BC, AC As Single
    
    ' Get values from text boxes
    AB = Val(Txt_AB.Text)
    BC = Val(Txt_BC.Text)
    AC = Val(Txt_AC.Text)
    
    ' Calculate the missing side
    If AB <> 0 And BC <> 0 Then
        AC = Sqr(AB ^ 2 + BC ^ 2)
        Txt_AC.Text = Round(AC, 2)
    ElseIf AB <> 0 And AC <> 0 Then
        BC = Sqr(AC ^ 2 - AB ^ 2)
        Txt_BC.Text = Round(BC, 2)
    ElseIf BC <> 0 And AC <> 0 Then
        AB = Sqr(AC ^ 2 - BC ^ 2)
        Txt_AB.Text = Round(AB, 2)
    Else
        MsgBox "Please enter any two sides", vbExclamation
    End If
End Sub

Explanation:

The code first retrieves values from three text boxes (Txt_AB, Txt_BC, Txt_AC)
It checks which two sides have values entered
Calculates the missing side using Pythagoras Theorem
Displays the result rounded to two decimal places
Shows a message if less than two values are entered

VB.NET Implementation

This VB.NET code provides the same functionality with modern .NET features:

Private Sub CalculateButton_Click(sender As Object, e As EventArgs) Handles CalculateButton.Click
    Dim AB, BC, AC As Double
    
    ' Try to parse the input values
    Dim abValid = Double.TryParse(txtAB.Text, AB)
    Dim bcValid = Double.TryParse(txtBC.Text, BC)
    Dim acValid = Double.TryParse(txtAC.Text, AC)
    
    ' Count how many sides were entered
    Dim enteredSides = If(abValid, 1, 0) + If(bcValid, 1, 0) + If(acValid, 1, 0)
    
    If enteredSides < 2 Then
        MessageBox.Show("Please enter at least two sides", "Input Error", 
                        MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Return
    End If
    
    ' Calculate the missing side
    If abValid AndAlso bcValid Then
        AC = Math.Sqrt(AB * AB + BC * BC)
        txtAC.Text = Math.Round(AC, 2).ToString()
    ElseIf abValid AndAlso acValid Then
        BC = Math.Sqrt(AC * AC - AB * AB)
        txtBC.Text = Math.Round(BC, 2).ToString()
    ElseIf bcValid AndAlso acValid Then
        AB = Math.Sqrt(AC * AC - BC * BC)
        txtAB.Text = Math.Round(AB, 2).ToString()
    End If
End Sub

Improvements in VB.NET version:

Uses Double.TryParse for safer input handling
Implements proper input validation
Uses Math.Sqrt and Math.Round from .NET Framework
Includes more user-friendly error messages
Follows modern event handling pattern

Practice Exercise

Enhance the Calculator

Try extending the Pythagoras Theorem calculator with these features:

Add unit selection (cm, m, inches, feet)
Implement input validation to prevent negative numbers
Add a visual indicator when the values form a Pythagorean triple (e.g., 3-4-5)
Create a history feature to remember previous calculations
Add an option to calculate the area of the triangle

Advanced Challenge: Create a graphical representation of the triangle that scales based on the entered values.