Function Secante(a As Double, b As Double, xtol As Double, ytol As Double, Nimax As Long) As Double

    Dim fa, fb, fc, c As Double
    Dim i As Long
    
    fa = fu(a)
    fb = fu(b)
    c = b - fb * (b - a) / (fb - fa)
    fc = fu(c)
    i = 0
    
    Do While Abs(c - b) >= xtol And Abs(fc) >= ytol And i <= Nimax
        
        a = b
        fa = fb
        b = c
        fb = fc
        c = b - fb * (b - a) / (fb - fa)
        fc = fu(c)
        i = i + 1
    Loop
    
    MsgBox "Número de iteraciones" + Str(i)
    
    
    Secante = c


End Function