Программа для вычисления определенного интеграла методом трапеций

Private Sub Command1_Click()
Dim s!, pi!, x!, r!, n!, f1!, f2!
pi = Atn(1) * 4
n = Val(InputBox("shag")) ' øàã èíòåãðèðîâàíèÿ
r = Val(InputBox("radius")) ' ðàäèóñ êðóãà
s = 0
For x = 0 To r - n Step n
 f1 = Sqr(r * r - x * x)
 f2 = Sqr(r * r - (x + n) * (x + n))
 s = s + (f1 + f2) / 2 * n
Next x
s = s * 4 'âû÷åñëåííàÿ ïëîùàäü
MsgBox "ìåòîä òðàïåöèé =" & s & " ôîðìóëà ïëîùàäè êðóãà =" & pi * r * r 'ðåçóëüòàòû
End Sub

Private Sub Command1_Click()
Dim s!, x!, f1!, f2!
s = 0
For x = 2 To 1.2 Step -0.001
 f1 = Sin(x) / x ^ 2
 f2 = Sin(x + 0.001) / (x + 0.001) ^ 2
 s = s + (f1 + f2) / 2 * 0.001
Next x
MsgBox "Îïðåäåëåííûé èíòåãðàëë = " & s
End Sub

Private Sub Command1_Click()
Dim s!, x!, f1!, f2!
s = 0
For x = 1 To 2 Step 0.014
f1 = x^3/(3+x)
f2 = (x+0.014)^3/(3+x+0.014)
s = s + (f1 + f2) / 2 * 0.014
 
Next x
MsgBox "Определенный интегралл = " & s
End Sub