nemo311
幼苗
共回答了3个问题 举报
(1-cot^4 A)sin^2 A+cot^2 A
=(1+cot^2 A)(1-cot^2 A)sin^2 A+cos^2 A/sin^2 A
=(sin^2 A/sin^2 A+cos^2 A/sin^2 A)(sin^2 A/sin^2 A-cos^2 A/sin^2 A)sin^2 A+cos^2 A/sin^2 A
=1/sin^2 A·[(sin^2 A-cos^2 A)/sin^2 A]·sin^2 A+cos^2 A/sin^2 A
=1
1年前
1