Re: [理工] [工數]-向量面積分
※ 引述《makoto1016 (makoto1016)》之銘言:
: Evaluate the surface integral ∫∫F.n da ,where F=(y^3,x^3,z^3)
: surface S:x^2+4y^2=1 , x≧0 y≧0 0≦z≦h
^
x = rcosθ , y = 0.5rsinθ , n =r = (cosθ,0.5sinθ,0)
∫∫F.n da = ∫∫F.r *rdθdz ︱r=1
= ∫∫(0.5)^3sin^3π*cosθ + 0.5*cos^3θ*sinθ dθdz
= h/32 sin^4θ︱ - h/8cos^4θ︱
sinθ:0~1 cosθ:1~0
= 5h/32
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