def task5(b: float) -> str:
    """
    Function that calculates area of an equilateral triangle. Suare root of 3 is 1.732. It returns the area as string
    that has two numbers after comma.

    Input: N -> float number
    Output: area of triangle as string such as: "1.23"
    """
    pole = (1.732/2) * b ** 2
    pole_str = f"{pole:.2f}"
    return pole_str