Private Sub Command1_Click()
    'PROGRAM D5R7
    'Driver for routine CHDER
    NVAL = 40
    PIO2 = 1.5707963
    Dim C(40), CDER(40)
    A = -PIO2
    B = PIO2
    Call CHEBFT(A, B, C(), NVAL)
    'Test derivative
    Print
    Print Tab(5); "How many terms in Chebyshev evaluation?"
    'Input MVAL , between 6 and 40, MVAL=0 TO END
    MVAL = 20
    Print Tab(5); MVAL
    If (MVAL <= 0) Or (MVAL > NVAL) Then Exit Sub
    Call CHDER(A, B, C(), CDER(), MVAL)
    Print Tab(5); "    X         Actual       Cheby. Deriv."
    For I = -8 To 8 Step 1
        X = I * PIO2 / 10#
        Print Tab(5); Format$(X, "#0.000000");
        Print Tab(19); Format$(FDER(X), "#0.000000");
        AAA = CHEBEV(A, B, CDER(), MVAL, X)
        Print Tab(34); Format$(AAA, "#0.000000")
    Next I
End Sub
Function FUNC(X)
    FUNC = (X ^ 2) * (X ^ 2 - 2#) * Sin(X)
End Function
Function FDER(X)
    'Derivative of FUNC
    AAA = 4# * X * ((X ^ 2) - 1#) * Sin(X)
    FDER = AAA + (X ^ 2) * (X ^ 2 - 2#) * Cos(X)
End Function