Elipse [0,2pi]
x=acosT
y=bsinT\
by symmetry
4I(y,x)
chossing the limits of integration my text is showing
4I(y,x,0,a)
T=0=>x=a
T=pi/2=>x=0
so wouldn't this be 4I(y,x,a,0)
proceeding inthe books case gives pi(ab) while in the later case gives -pi(ab)
Also
x= (t-1)/t y=(t+1)/t...