求定积分∫ 根号(1-x^2)dx(上下限0—1/2)

设x = siny,dx = cosy dy当x = 0,y = 0；当x = 1/2,y = π/6∫(0→1/2) √(1 - x²) dx= ∫(0→π/6) √(1 - sin²y) • cosy dy= ∫(0→π/6) cos²y dy= (1/2)∫(0→π/6) (1 + cos2y) dy= (1/2)...