正在做啊〔sin（a＋9π/2）/1－tan∧2（3π/2－a）〕－〔sin（a－11π）/1－cot∧2（5π/2＋a）〕=[cosa/(1-cot^2a)]-[-sina/(1-tan^2a)]=cosa/(1-cos^2a/sin^2a)+sina/(1-sin^2a/cos^2a)=sin^2acosa/(sin^2a-cos^2a)+sinacos^2a/(cos^2a-sin^2a)=sinacosa(sina-cosa)/(sin^2a-cos^2a)=sinacosa/(sina+cosa)=(m/2)/(-(根号2+1)/2)=m/(根号2+1)=m(根号2-1)=(m/2)/(-(根号2+1)/2)=-m/(根号2+1)=-m(根号2-1)