human
2d vector rotate angle.
assistant
Here is a Python function to 2d vector rotate angle

import numpy as np

def rotate_angle(v, angle):
    """Rotate 2d vector v by angle.
    """
    vx = v[0]
    vy = v[1]
    vx2 = vx * np.cos(angle) - vy * np.sin(angle)
    vy2 = vx * np.sin(angle) + vy * np.cos(angle)
    return np.array([vx2, vy2])

# Enter the vector
v = np.array([1, 2])

# Enter the angle
angle = 0.5

# Calling the function
print((rotate_angle(v, angle)))

#Example Output
# [-0.08126852  2.23459066]

#Remember to inspect code for bugs.