tanα＋1÷tan﹙π÷4＋α÷2﹚
=tanα+1/tan(π/4+α/2)
=sinα/cosα+cos(π/4+α/2)/sin(π/4+α/2)
=sinα/cosα+[(cos(α/2)-sin(α/2)]/[cos(α/2)+sin(α/2)]
=sinα/cosα+[cos(α/2)-sin(α/2)]^2/{[cos(α/2)]^2-[sin(α/2)]^2}
=sinα/cosα-[1-2sin(α/2)cos(α/2)]/cosα
=sinα/cosα-(1-sinα)/cosα
=1/cosα第三個(gè)等號到第四個(gè)等號中的分母怎么得到=sinα/cosα+[(cos(α/2)-sin(α/2)]/[cos(α/2)+sin(α/2)]=sinα/cosα+[cos(α/2)-sin(α/2)]^2/{[cos(α/2)]^2-[sin(α/2)]^2}分子、分母同乘以[cos(α/2)-sin(α/2)]