问TypeError:无法将序列乘以'float‘| Python类型的非整数

EN

h = s * math.tan(a * 3.14/180) - g * s * s / (v**2 * math.cos(a*3.14/180)**2 * 2)

TypeError: can't multiply sequence by non-int of type 'float'

import math

g = 9.81
s = 25
v = float(txtv.get())
a = float(txta.get())
h = s * math.tan(a * 3.14/180) - g * s * s / (v**2 * math.cos(a*3.14/180)**2 * 2)


window = Tk()  
window.title("Добро пожаловать в приложение PythonRu")  
window.geometry('400x250')  
lbls = Label(window, text="Ввод переменной S:")  
lbls.grid(column=0, row=0)  
txts = Entry(window,width=10)  
txts.grid(column=1, row=0)  

lblv = Label(window, text="Ввод переменной Vo:")  
lblv.grid(column=0, row=1)  
txtv = Entry(window,width=10)  
txtv.grid(column=1, row=1)  

lbla = Label(window, text="Ввод переменной a:")  
lbla.grid(column=0, row=2)  
txta = Entry(window,width=10)  
txta.grid(column=1, row=2)