cos α =t_(x)/sqrt(t^2_(x)+t^2_(y))
cos β =t_(y)/sqrt(t^2_(x)+t^2_(y))
Так как
cos α =3/sqrt(3^2+2^2)=3/sqrt(13)
cos β =2/sqrt(3^2+2^2)=2/sqrt(13)
z`_(x)=y*/(1+(sqrt(lnx))^2)*(sqrt(lnx))`_(x)=
=y/((1+lnx)*2sqrt(lnx))*(lnx)`=y/(2x*(1+lnx)*sqrt(lnx))
z`_(y)=arctg sqrt(lnx)
z`_(x) (M)=1/(4*(1+ln2)*sqrt(ln2))
z`_(y)(M)=arctgsqrt(ln2))
z`_(t)(M)=z`_(x)(M)cos α +z`_(y)(M)cos β
z`_(t)(M)= 3/(4*sqrt(13)*(1+ln2)*sqrt(ln2)) + 2*(arctgsqrt(ln2))/sqrt(13) - о т в е т.