Calcolare intD (xy) dxdy
dove
D = {(x, y) in R2 | x >= 0, y <= sqrt(3)x, y < 1/x, y >= x}
Soluzione.
Si ha
intD xy dxdy = int01/sqrt(3) x (intxsqrt(3)x y dy) dx + int1/sqrt(3)1 x (intx1/x y dy) dx =
= int01/sqrt(3) x (y2/2)|xsqrt(3)x dx + int1/sqrt(3)1 x (y2/2)|x1/x dx = int01/sqrt(3) x3 dx + int1/sqrt(3)1 (1/2x - x3/2) dx =
= (x4/4)|01/sqrt(3) + (1/2 log x - x4/8)|1/sqrt(3)1 = 1/12 + (-1/8 + 1/8 log 3 + 1/24) = 1/8 log 3.