解:dx/dt=-sint; dy/dt=cost, dz/dt=sint+cost; 过点P1(1/√2,1/√2,2)的切向量为
→v={-1/√2,1/√2,√2} 。∂f/∂x=6x^2, ∂f/∂y=e^z, ∂f/∂z=ye^z-1/(1+z); 过点:(1.2.0)的:法向量为:→n={6,1,1} ;所求平面的法向量为:→np=(→v)X(→n)={(1/√2)*1-√2*1,√2*6-(-1/√2)*1,(-1/√2)*1-1/√2*6}={-√2/2,13√2/2,-13√2/2}; 所求的方程为:
-√2/2(x-1)+13√2/2(y+1)-13√2/2(z-2)=0,方程两边同时除以(-√2/2),得平面方程为:
(x-1)-13(y+1)+13(z-2)=0;整理,得:x-13y+13z-40=0