pythonでコーディングしていて"float object can not callable"というエラーが出たのですがどのように変更すればよいのでしょうか

pythonで数値計算のプログラムを書いているのですが、

terminal
1Traceback (most recent call last):
2  File "task.py", line 35, in <module>
3    x_2d, x1, x2 = fd(t, x_2d)
4  File "task.py", line 14, in fd
5    A_2d = np.array([[x2_now], [u(t)]])

という風にエラーが出てしまうのですが、どこを変更すればよいのでしょうか。

python
1#coding utf-8
2import math
3import numpy as np
4import matplotlib.pyplot as plt
5
6def u(t):
7    P = np.pi
8    u_cul = (1.0/0.159103) * math.sin(2.0*P*t)
9    return u_cul
10
11def fd(t, x_2d):
12    x2_now = x_2d[1][0]
13    A_2d = 0.0
14    A_2d = np.array([[x2_now], [u(t)]])
15
16    dx1_2d = DT * A_2d / 6.0
17    dx2_2d = DT * A_2d / 3.0
18    dx3_2d = DT * A_2d / 3.0
19    dx4_2d = DT * A_2d / 6.0
20    dx_2d_sum = dx1_2d + dx2_2d + dx3_2d + dx4_2d
21    x_2d = x_2d + dx_2d_sum
22    return x_2d, x_2d[0][0], x_2d[1][0]
23
24
25DT = 0.01
26t = 0.0
27x_2d = np.array([[0.0], [0.0]])
28t_list = []
29x1_list = []
30x2_list = []
31u_list = []
32
33for i in range(0,101):
34    t_list.append(t)
35    x_2d, x1, x2 = fd(t, x_2d)
36    u = u(t)
37    x1_list.append(x1)
38    x2_list.append(x2)
39    u_list.append(u)
40    t = t + DT
41
42
43plt.plot(t_list, u_list, c='green', label='u')
44plt.plot(t_list, x1_list, c='blue', label='x1')
45plt.plot(t_list, x2_list, c='red', label='x2')
46
47plt.title('', fontsize = 20)
48plt.xlabel('t', fontsize = 16)
49plt.ylabel('x', fontsize = 16)
50plt.tick_params(labelsize=14)
51plt.grid(True)
52plt.legend()
53plt.show()