积分符号 0到pai/2 dx/(cosx+2)
问题描述：
积分符号 0到pai/2 dx/(cosx+2)
答
∫[0,π/2] dx/(cosx+2) 令x=2t = ∫[0,π/4] 2/(2+cos2t) dt =∫[0,π/4] 2/ [1+2(cost)^2]dt 上下同除(cost)^2=∫[0,π/4] 2(sect)^2 / [2+(sect)^2]dt =∫[0,π/4] 2 / [2+(sect)^2] dtant =∫[0,π/4] 2 / [3+(t...