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sinπ/8×sinπ5/8=

sinπ/8×sinπ5/8=sinπ/8sinπ3/8 =sinπ/8cosπ/8 =1/2sinπ/4 =1/2*√2/2 =√2/4 望采纳

因为sin(5/8π+μ)=1, 所以5/8π + u=π/2 + 2kπ(k为整数) u=-π/8 + 2kπ(k为整数)

1。t*π/8=2π,解得t=16(s) 2。把t=2和t=20分别代入等式,得出的两个便是所求的高度 3。sin函数不管变量如何表示,最大值为1,最小值为-1,所以5sinπ/8 t的最大值为5,最小值喂-5,所以落差为5-(-5)=10米

sin(5π/8)=cos(π/8)? 解:sin(5π/8)=sin(π/2+π/8)=cos(π/8),故正确!

sin(5π/8) =cos(π/2 -5π/8) =cos(π/8) = √{ [1+ cos(π/4)]/2 } = √{ [1+ √2/2]/2 } =√(2+√2) /2

f(x)= 2cos(x-π/3)+2sin(3π/2-x) =2cos(x-π/3)-2cosx =2(cosxcosπ/3+sinxsinπ/3)-2cosx =√3sinx+cosx-2cosx =√3sinx-cosx =2(sinxcosπ/6-cosxsinπ/6) =2sin(x-π/6)

由sinacosa=1/8得 (cosa-sina)^2=(cosa)^2-2sinacosa+(sina)^2 =(cosa)^2+(sina)^2-2sinacosa =1-2*1/8 =3/4 所以cosa-sina=(3/4)开根号=2分之根号3 或等于负的2分之根号3 由于π/4小于a小于π/2 则cosa

这五个点分别是(0,1)(π/4,2)(π/2,1)(3π/4,0)(π,1),然后顺次光化曲线连接起来即可。

① arcsin[cos(-7π/6)] =arcsin[cos(-π-π/6)] =arsin(-cosπ/6) =arcsin(-√3/2) =-π/3 ② 设α=arcsin3/5, β=arcsin8/17, α,β均是锐角 那么sinα=3/5,cosα=4/5 sinβ=8/17,cosβ=15/17 ∴sin(arcsin3/5+arcsin8/17) =sin(α+β) =sinαcosβ+cosαsinβ...

cos(5π/8) × cos(π/8) =[cos(π/2+π/8)]×cos (π/8) =-sin(π/8)×cos (π/8)----公式:cosπ/2+a=-sina =-1/2 × 2sin(π/8)×cos (π/8) -----后面的2sincos用2倍角公式合并 =-1/2 × sin (π/4) =-1/2 × √2/2 =-√2/4

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