(x^2+y^2)^2=a^2(2x^2+3y^2)
y=rsin
x^2+y^2=r^2
r^4=a^2*r^2(2cos^2φ +3sin^2φ )
r^2=a^2(2cos^2φ +3sin^2φ )
r=asqrt(2cos^2φ +3sin^2φ )- уравнение данной кривой
в полярных координатах
0 ≤ φ ≤ 2π
S= ∫ ∫ _(D)dxdy=
= ∫ ^( 2π)_(0)( ∫^(asqrt(2cos^2φ +3sin^2φ )) _(0)asqrt(2cos^2φ +3sin^2φ )dr)d φ =
= ∫ ^( 2π)_(0) asqrt(2cos^2φ +3sin^2φ )*r |^(asqrt(2cos^2φ +3sin^2φ )) _(0)d φ =
=a^2 ∫ ^( 2π)_(0) (2cos^2φ +3sin^2φ)d φ =
[ 2cos^2 φ +2sin^2 φ =1 ]
=a^2 ∫ ^( 2π)_(0) (2 + sin^2φ)d φ =
[sin^2 φ =(1-cos2 φ )/2]=
=a^2 ∫ ^( 2π)_(0) ((5/2)-(1/2)cos2 φ)d φ =
=a^2 * ((5/2) φ -(1/4)sin2 φ)|^( 2π)_(0)=5*πa^2