2-16 设已求得一点处的应力分量,试求σ1,σ 2,α1:-|||-(a) (sigma )_(x)=100 ,σy=50, _(xy)=10sqrt (50);-|||-(b) (sigma )_(x)=200 ,σy=0, _(xy)=-400;-|||-(c) (sigma )_(x)=-2000 _(y)=1000 _(xy)=-400;-|||-(d) (sigma )_(x)=-1000 _(y)=-1500 _(xy)=500