# Thread: average valua of f(x,y)

1. ## average valua of f(x,y)

f(x,y)=1/(xy); nn2<= X<=2; ln2<=y<=2ln2

the answer is shown in the attached file but i dont understand the circled value
thank you

2. The average of $f(x)$ on the interval $[a,b]$ is

$\frac{1}{b-a}\int_a^bf(x) \ dx$

The average of $f(x,y)$ on the square $[a,b] \times [c,d]$ is

$\frac{1}{(b-a)(d-c)}\int_c^d\int_a^bf(x,y) \ dx\ dy$