=∫sint/cost dt
=∫1/cost d(-cost)
因为∫sintdt=-cost(sint的不定积分)
所以sintdt=d(-cost)
=-∫1/cost d(cost)(换元积分法)
令u=cost,du=d(cost)
=-∫1/u du=-ln|u|+C
=-ln|cost|+C
匿名回答于2024-06-07 08:46:25