曲线x＝t-sint,y＝1-cost,z＝4sin（t/2）在点（π/2-1,1,2√2）,对应参数值 t = π/2
切向量 T = ( x'(t),y'(t),z'(t) ) | t=π/2
= ( 1-cost,sint,2 cos(t/2) ) | t=π/2
= (1,1,√2 )
切线方程 x - (π/2-1) = y - 1 = (z - 2√2) / √2
法平面方程 x - (π/2-1) + y - 1 +√2 (z - 2√2) = 0
即 x + y + √2 z - π/2 - 4 = 0