cos^4(π/8)-sin^4(π/8)等于?
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cos^4(π/8)-sin^4(π/8)等于?
cos^4(π/8)-sin^4(π/8)等于?
cos^4(π/8)-sin^4(π/8)等于?
cos^4(π/8)-sin^4(π/8)
[平方差公式]
=(cos^2(π/8)-sin^2(π/8))(cos^2(π/8)+sin^2(π/8))
=(cos^2(π/8)-sin^2(π/8))*1
[2倍角公式 cos^2(a)-sin^2(a)=cos2a]
=cos(π/8*2)
=cos(π/4)
=根号2/2
化简sin(α-5π)/cos(3π-α)×cos(π/2-α)/sin(α-3π)×cos(8π-α)/sin(-α-4π)
cos^6(π/8)-sin^6(π/8)=求值,[cos^2(π/8)-sin^2(π/8)][cos^4(π/8)+sin^4(π/8)+cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-[sin^2(π/4)]/4]==7√2/16
sin^4π/8 +cos^4π/8
(cos(π/8))^4-(sin(π/8))^4
sin^4π/8-cos^4π/8=?
cos^4(π/8)-sin^4(π/8)等于?
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