Next the program lets t (theta) run over the values needed for the curve in small increments. For this equation, 0 <= t <= 2 * PI. It uses the value of t to calculate r.

Next the program converts the polar coordinates (r, t) into cartesian coordinates (x, y) where:

x = r * Cos(t)
y = r * Sin(t)

The program connects the points to draw the curve.

Private Sub DrawCurve()
Const PI = 3.14159265
Dim A As Single
Dim B As Single
Dim x As Single
Dim y As Single
Dim r As Single
Dim t As Single
Dim dt As Single

    picGraph.AutoRedraw = True
    picGraph.Cls

    A = CSng(txtA.Text)
    B = CSng(txtB.Text)

    ' Set a convenient scale.
    If A < B Then
        picGraph.ScaleLeft = -1 - 0.25
        picGraph.ScaleWidth = 1 + A + B + 0.5
    Else
        picGraph.ScaleLeft = B - A - 0.25
        picGraph.ScaleWidth = 2 * A + 0.5
    End If
    picGraph.ScaleLeft = picGraph.ScaleLeft * 1.5
    picGraph.ScaleWidth = picGraph.ScaleWidth * 1.5
    picGraph.ScaleTop = picGraph.ScaleWidth / 2
    picGraph.ScaleHeight = -picGraph.ScaleWidth

    ' Draw axes.
    picGraph.Line (picGraph.ScaleLeft, _
        0)-Step(picGraph.ScaleWidth, 0), vbBlue
    x = Int(picGraph.ScaleLeft)
    Do While x <= picGraph.ScaleLeft + picGraph.ScaleWidth
        picGraph.Line (x, -0.2)-(x, 0.2), vbBlue
        x = x + 1
    Loop

    picGraph.Line (0, picGraph.ScaleTop)-Step(0, _
        picGraph.ScaleHeight), vbBlue
    y = Int(picGraph.ScaleTop)
    Do While y >= picGraph.ScaleTop + picGraph.ScaleHeight
        picGraph.Line (-0.2, y)-(0.2, y), vbBlue
        y = y - 1
    Loop

    picGraph.Line (0, -5)-(0, 5), vbBlue
    For y = -5 To 5
        picGraph.Line (-0.2, y)-(0.2, y), vbBlue
    Next y

    ' Draw the parametric curve.
    t = 0
    dt = PI / 100
    r = A + B * Cos(t)
    picGraph.CurrentX = r * Cos(t)
    picGraph.CurrentY = r * Sin(t)

    Do While t <= 2 * PI
        r = A + B * Cos(t)
        x = r * Cos(t)
        y = r * Sin(t)
        picGraph.Line -(x, y)
        t = t + dt
    Loop

    t = 0
    r = A + B * Cos(t)
    picGraph.CurrentX = r * Cos(t)
    picGraph.CurrentY = r * Sin(t)
    picGraph.Line -(x, y)
End Sub