帮忙求一个积分~

∫cosα/(d+Rsinα)dα
=∫dsinα/(d+Rsinα)
=1/R*∫d(Rsinα)/(d+Rsinα)
=1/R*∫d(d+Rsinα)/(d+Rsinα)
=1/R*ln(d+Rsinα)
=1/R*[ln(d+Rsin2π)-ln(d+Rsin0)]
=1/R*(lnd-lnd)
=0

∫cosα/(d+Rsinα)dα=∫/(d+Rsinα)dsinα
=(1/R)∫1/ (d+Rsinα)d(Rsinα+d)
=(1/R)ln(d+Rsinα)|0,2π
=（1/R）lnd-(1/R)lnd
=0

原式等于∫[1／(D+Rsinα)]dsinα＝(1／R)∫[1／(D+Rsinα)]d(D+Rsinα)=(1／R)ln(D+Rsinα) 然后把上下限代进去，结果为零。