由于b+π/4 = (a+b) - (a-π/4)
所以tan(b+π/4) = tan[(a+b) - (a-π/4)] = [tan(a+b) - tan(a-π/4)] / [1 + tan(a+b) * tan(a-π/4)]
=(5/3) / (1 + 4) = 1/3太给力了，你的回答完美解决了我的问题！