∫∫ e^(x²+y²) dxdy =∫∫ e^(r²)*r drdθ =∫[0→2π]dθ∫[0→2] e^(r²)*r dr =2π∫[0→2] e^(r²)*r dr =π∫[0→2] e^(r²) d(r²) =πe^(r²) |[0→2] =π(e^4-1)
