令t = 1/y,y = 1/t,sin(1/y) = sint
y² = 1/t²,dy = -dt/t²
1/y = 2／π,t = π／2
1/y = 1/π,t = π
原积分变为∫(t²sint)(-dt/t²) = -∫sintdt = cost + C
积分区间为π到π/2,结果为1
令t = 1/y,y = 1/t,sin(1/y) = sint
y² = 1/t²,dy = -dt/t²
1/y = 2／π,t = π／2
1/y = 1/π,t = π
原积分变为∫(t²sint)(-dt/t²) = -∫sintdt = cost + C
积分区间为π到π/2,结果为1