已知f（x）=lnx+cosx，则f′(π2)=．

Question

已知f（x）=lnx+cosx，则f′((π)/(2))=______．

Answer 1

f′(x)＝−sinx+(1)/(x)，∴f′((π)/(2))＝−1+(2)/(π)，
故答案为：(2)/(π)−1．