<human>:  2d vector rotate angle.
<bot>: Here is a Python code to 2d vector rotate angle

import math

def rotate_angle(vector, angle):
  """
  Rotate a 2d vector by a given angle.
  """
  x, y = vector
  x_new, y_new = x * math.cos(angle) - y * math.sin(angle), x * math.sin(angle) + y * math.cos(angle)
  return (x_new, y_new)

# Enter the vector
vector = (1, 2)

# Enter the angle
angle = math.pi / 4

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

#Example Output
# (-0.7071067811865474, 2.121320343559643)

#Remember to inspect code for bugs.