csc(x)/sin(x)-(cot(x)csc(x))/sec(x)=1/sin²(x) - sin(x)/cos(x)*1/sin(x) *cos(x)=1/sin²(x)-1=(1-sin²(x))/sin²(x)=cos²(x)/sin²(x)=cot²(x) 哪一步不明白,可以追...第一步的cot(x)為什么會變成sin(x)/cos(x)呢?公式的cot(x)=cos(x)/sin(x)?寫反了 csc(x)/sin(x)-(cot(x)csc(x))/sec(x) =1/sin²(x) - cos(x)/sin(x)*1/sin(x) *cos(x) =1/sin²(x)- cos²(x)/sin²(x) =(1-cos²(x))/sin²(x) =sin²(x)/sin²(x) =1這回對了還有問題么？謝謝你:)