※ 引述《ROGER2004070 (RR)》之銘言：
: The area enclosed by the plane curve x2 +xy+y2 -1=0
: 不知如何下手 麻煩高手了...
我又想到一招了..
let x = a+b y = a-b
x^ + xy + y^2 = 1
-> 3a^2 + b^2 = 1
-> jacobin = 2
1
∫∫2 dA = 2∫ (-b)da + (a)db let a=---cost b=sint
A C √3
2π 1 1
= 2∫ (-sint)---(-sint)dt + ---cost costdt
0 √3 √3
4√3
= ------π
3
2√3
A = ------π
3
--
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