Результат функции (calculate) выдает неверный результат.

[trfioodim]

from tkinter import *
from math import *

def calculate():
Alfa = alfaEntry.get()
Gamma = gammaEntry.get()
S = SEntry.get()
d0 = (S * cos((Alfa - 2.5) * pi/180)) /(pi * sin((Alfa - 2.5) * pi/180))
angleLabel.configure(text = d0)

window = Tk()
window.title("Cutting")
window.geometry('1000x1000')


lblTitle = Label(window, text = "Test №1. Trifonov. ET1-61. Variant №33.")
lblTitle.grid(column = 0, row = 0)
lblOccurateData = Label(window, text = "Initial data: ")
lblOccurateData.grid(column = 0, row = 1)
lblInput = Label(window, text =" alfa = 5 deg, gamma = 15 deg, S = 0,4 mm/rot.")
lblInput.grid(column = 0, row = 2)

lblAlfa = Label(window, text = "Alfa = ")
lblAlfa.grid(column = 0, row = 3)
alfaEntry = Entry(window, width = 20)
alfaEntry.grid(column = 1, row = 3)

lblGamma = Label(window, text = "Gamma = ")
lblGamma.grid(column = 0, row = 4)
gammaEntry = Entry(window, width = 20)
gammaEntry.grid(column=1, row = 4)

lblS = Label(window, text = "S = ")
lblS.grid(column = 0, row = 5)
SEntry = Entry(window, width = 20)
SEntry.grid(column = 1, row = 5)

calculationButton = Button(window, text = "Calculate", width = 20, command = calculate)
calculationButton.grid(column = 0, row = 6)

workLabel = Label(window, text = "Workpiece diameter: ")
workLabel.grid(column = 0, row = 7)

angleLabel = Label(window)
angleLabel.grid(column = 1, row = 7)

alfaEntry = DoubleVar()
gammaEntry = DoubleVar()
SEntry = DoubleVar()


window.mainloop()