Verified answer

m = ∫ ∫ ρ(x,y) dA

m = π ∫ ∫ x dy[0,sin(x)] dy[0,π/2]

m = π ∫ x∙sin(x) dy[0,π/2]

m = π [ -x∙cos(x) | (0,π/2) + ∫ cos(x) dx[0,π/2] ]

m = π [sin(π/2) - sin(0)]

m = π