import math


def calc_b(degrees_a, hypotenuse):
    """
    计算直角三角形的B边
         ∠b
          *
        A *  *   C
          *    *
       ∠c ******** ∠a
            B
    :param degrees_a: A角
    :param hypotenuse: 斜边
    :return: B边长度
    """
    return math.cos(math.radians(degrees_a)) * hypotenuse