cosα的四次方-sinα的四次方_数学解答

cosα的四次方-sinα的四次方

人气：191 ℃　时间：2020-01-28 03:49:08

解答

(cosα)^4-(sinα)^4
=[(cosα)^2+(sinα)^2][(cosα)^2-(sinα)^2]
=1*[(cosα)^2-(sinα)^2]
=cos2a