$\int_{]a_1, b_1] \times ]a_2, b_2]} f \, d\lambda^2 = \int_{a_2}^{b_2} \int_{a_1}^{b_1} f(x_1, x_2) \, dx_1 \, dx_2$
f is continous function from R^2 to R. I have to show the equation above. My question is: isnt this Fubinis theorem or can i apply fubini on the LHS?