作者gogoabc (小多爱喝养乐多)
看板trans_math
标题[积分] 椭圆参数方程式积面积
时间Sun Apr 12 22:05:02 2009
x=acosΘ
y=bsinΘ
求Θ 从0~2π所围的面积
sol:
0
A=4∫ydx=4∫bsinθ(-asinθ)dθ =πab
π/2
为什麽上下限是从π/2积到0????
难道是因为从0积到π/2会变负???应该不是这样解释吧 请问要怎麽解释呢??
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 118.160.160.136
1F：→ Qmmm:因为没加绝对值 219.70.179.240 04/12 22:32
2F：→ fong1014:ydx，上下界是从0积到b，x=0 Θ=(π/2) 61.228.8.174 04/13 01:40
3F：→ fong1014:同样，x=a Θ=0 ....上行手误,从0积到a 61.228.8.174 04/13 01:42