Encontrar las primeras derivadas parciales paras siguientes funciones

a) ? (?, ?) =sin [x/(1+y)]

∂f(x,y)/∂x= cos[x/(1+y)] / (1+y):

∂2f(x,y)/∂x^2 = [1/(1+y)]* (-sen)[x/(1+y)] / (1+y);  o:

∂2f(x,y)/∂x^2 = [(-1)/(1+y)^2]* sen[x/(1+y)];

∂f(x,y)/∂y = cos[x/(1+y)] * [(-x)/(1+y)^2];

∂2f(x,y)/∂y^2 = (-sen)[x/(1+y)]*[(-x)/(1+y)^2]^2 + {cos[x/(1+y)]*[2(1+y)x]/(1+y)^4}: 

∂2f(x,y)/∂y^2 = (-sen)[x/(1+y)]*[(-x)/(1+y)^2]^2 + {cos[x/(1+y)]*2x]/(1+y)^3}

b) ? (?, ?, ?) =?y/z

∂f(x,y,z)/∂x = (y/z)

∂2f(x,y,z)/∂x^2 = 0;

∂f(x,y,z)/∂y = (x/z);

∂2f(x,y,z)/∂y^2 = 0;

∂f(x,y,z)/∂z = (-xy)/z^2;

∂2f(x,y,z)/∂z^2 = 2xy / z^3