cos^6(π/8)-sin^6(π/8)=
来源:百度知道 编辑:UC知道 时间:2024/05/26 15:24:46
求值,要过程
[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
[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
先用平方差公式从六次化作三次,化简后在用立方差公式,应该能算吧!我手机不好输过程……
cos^6(π/8)-sin^6(π/8)
=1/2cos^3(π/4)-1/2sin^(π/4)
因为 cosπ/4=sinπ/4 所以为0
cos^6(π/8)-sin^6(π/8)
=【cos^3(π/8)】^2-【sin^3(π/8)】^2 (cos^2B-sin^2 B=cos(2B)
=cos^3(π/8+π/8)
=cos^3(π/4)
=(√2/2)^3
=√2/4
求值:cos(π/13)+cos(3π/13)+cos(9π/13)
cos(π/6-α)=m,m绝对值小于等于1,求cos(5π/6+α)
cos(π/2-α)=?
已知sinαcosα=-1/8 且α∈(π/2,3π/4) . 则sinα+cosα值为
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cos(73度)cos(73度)+cos(47度)cos(73度)+cos(47度)cos(47度)
cos(5*3.1415926..)/8 * cos (3.1415926../8)=多少
求值: 1-sin^6a-cos^6a/1-sin^4a-cos^4a
化简:(1-(sin a)^6-(cos a)^6)/(1-(sin a)^4-(cos a)^4)