x= ρ cos φ
y= ρ sin φ
0 ≤ ρ ≤ 1
0 ≤ φ ≤ π/2
arctg(y/x)=arctg(sin φ /cos φ )=arctg(tg φ )= φ
dxdy= ρ d ρ d φ
Получим
∫ ^(1)_(0)[blue][b]( ∫ ^(π/2)_(0) φ d φ )[/b][/blue]d ρ =∫ ^(1)_(0)[blue][b]( φ^2/2)| ^(π/2)_(0) )[/b][/blue]d ρ =[blue][b](π^2/8)[/b] [/blue] (ρ) |^(1)_(0)=π^2/8