import math


def R_iphase(h_i, radius, Theta):
    """ interafacial thermal resistance of a single drop
    
    Parameters
    ----------
    h_i:        float            
                interfacial heat transfer coefficient in MW/m²K
    radius:     float
                radius of drop in m
    Theta:      float    
                static contact angle in deg                   
    
    Returns
    ----------
    R_iphase:   float
                interafacial thermal resistance of drop in K/W
    """
    R_iphase = 1 / (2*h_i*1000*1000*math.pi*radius**2*(1-math.cos(math.radians(Theta))))
    return R_iphase