sina^4+cosa^4=(sina^2+cosa^2)-2sina^2cosa^2
=1-2[1-cos2a)/2]*[(1+cos2a)/2]
=1-(1-cos^2a)/2
=1-[1-(3/5)^2]/2
=1-8/25=17/25
已知cos2a=3/5,求sina^4+cosa^4的值
已知cos2a=3/5,求sina^4+cosa^4的值
问答人气:841 ℃时间:2024-05-13 04:23:46
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