s1 ='log(x^2+y^2)-sin(x*y)-log(2)-log(pi)';
s2='exp(x-y)+cos(x*y)';
n = 15; tor = 10^(-6) ;
a = [ 0.5 0] ;
newton(s1, s2, a , n, tor)
broyden(s1, s2, a , n, tor)