def rotate90_point(x, y, rotate90origin=()):
    """Rotates a point 90 degrees CCW in the x-y plane.

    Args:
        x, y (float): Coordinates.
        rotate90origin (tuple): x, y origin for 90 degree CCW rotation in x-y plane.

    Returns:
        xrot, yrot (float): Rotated coordinates.
    """

    # Translate point to origin
    x -= rotate90origin[0]
    y -= rotate90origin[1]

    # 90 degree CCW rotation and translate back
    xrot = -y + rotate90origin[0]
    yrot = x + rotate90origin[1]

    return xrot, yrot