angle correlation - combine method

import math

def q(r):
    return r*r

def deltaR(N,Nb,N1,N2,NB):
    a = q(math.sqrt(N)/((N1-NB)*(N2-NB)))
    b = q(math.sqrt(Nb)/((N1-NB)*(N2-NB)))
    c = q((N-Nb)*math.sqrt(N1)/((N2-NB)*q(N1-NB)))
    d = q((N-Nb)*math.sqrt(N2)/((N2-NB)*q(N1-NB)))

    return math.sqrt(a+b+c+d)

dR90 = deltaR(32,2,35735,36631,644)
dR135 = deltaR(41,2,34781,42108,644)
dR180 = deltaR(49,2,35323,45324,644)

R90 =2.40194e-08
R135= 2.74348e-08
R180= 3.04404e-08

K135 = R135/R90
K180 = R180/R90


print "dR(90) =",dR90
print "dR(135) =",dR135
print "dR(180) =" ,dR180

def deltaK(K,dR,R,R90,dR90):
    a = q(dR/R)
    b = q(dR90/R90)
    return K*math.sqrt(a+b)

dK135 = deltaK(K135,dR135,R135,R90,dR90)
dK180 = deltaK(K180,dR180,R180,R90,dR90)

print "dK(135) =",dK135
print "dK(180) =",dK180

da2 = math.sqrt(16*q(dK135)+q(dK180))
da4 = math.sqrt(16*q(dK135)+4*q(dK180))

print "da2 =",da2
print "da4 =",da4