var('x,y,z')
z=x+y*I
f=(I*z+2)/(3*z-6*I)
z=diff(f,x)
/*at any z result is 0*/
if(real_part(z)==imag_part(z)):/*explaination*/
    print "0"

Kreyszig-12.3-23-U (last edited 2010-12-18 05:41:33 by xxx)