
Yefim S. answered 11/18/19
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In polar coordinates x = rcosφ, y = rsinφ, x2 + y2 = r2. dA = dxdy = rdrdφ
Region is: 0≤r≤3, 0≤φ≤π.Our integral I = ∫∫sinr2rdrdφ =π∫sinr2rdr = π/2(-cosr2) with substitution from 0 to 3
I = -π/2(cos9 - cos0) = π/2(1-cos9)