∫[0,π²] sin√x dx 令√x=t ,则x=t² dx=2tdt∫[0,π²] sin√x dx=∫[0,π] (sint)2tdt=∫[0,π] 2td(-cost)=-2tcost|[0,π]+∫[0,π] 2costdt=-2πcosπ+2×0×cos0+ 2sint|[0,π]=2π+2sinπ-2sin...