∫xarccosx/√(1-x²) dx=-√(1-x²)*arccosx-x+C∴∫(0到π/2) xarccosx/√(1-x²) dx={-√[1-(π/2)²]*arccos(π/2)-π/2}-{-√(1-0²)*arccos0}=(-1/2)i√(π²-4)arccos(π/2)≈1.2395...