a11 =  cos(b)∗cos(c)
a12 = −cos(b)∗sin(c)
a13 =  sin(b)
a21 = cos(a)∗sin(c)+cos(c)∗sin(a)∗sin(b)
a22 = cos(a)∗cos(c)−sin(a)∗sin(b)∗sin(c)
a23 = −cos(b)∗sin(a)
a31 = sin(a)∗sin(c)−cos(a)∗cos(c)∗sin(b)
a32 = cos(c)∗sin(a)+cos(a)∗sin(b)∗sin(c)
a33 = cos(a)∗cos(b)

a = atan2(-a23,a33)
 b = atan2(a13, sqrt(a23^2+a33^2) )
 c = atan2(-a12,a11)