sin(30°—α)=1/4 sin(30°+2α)=?

sin(30°—α)=1/4 sin(30°+2α)=? 傅里叶级数作图f（x）=2sin[x] - sin[2x] + 2/3sin[3x] - 1/2sin[4x]我用mathematica输入程序Plot[{2sin[x],-2sin[x],2sin[x] - sin[2x],-2sin[x] + sin[2x],2sin[x] - sin[2x] + 2/3sin[3x],-2sin[x] + sin[2x] - 2/3sin[3x],2sin[x] - sin[2x] + 2/3si sin²1°+sin²2°+sin²3°+……+sin²87°+sin²88°+sin²89°= sin²1°+sin²2°+sin²3°+...+sin²88°+sin²89°+sin²90°=等于多少? 已知（tanα+1）/（tanα-1）=3,求下列各式的值1、（2sinα-3sinα)/(4sinα-9sinα)2、(sinα)^2-3sinα*cosα+1 若sin(α+β)=1/2,sinαcosβ=3/4,则sin(α-β)= 2sinα-3cosα/4sinα-9cosα=-1,则9sin^2α-3sinαcosα-5= 已知(tanα-3)(sinα+cosα +3)=0,求下列各式的值 4sinα-2sinα/5cosα+3sinα 2/3sin方α+1/4cos方α4sinα-2sinα/5cosα+3sinα2/3sin方α+1/4cos方α 为什么sin-sin^2=1/4 a/sinα=a+1/3sinα-4sin^3α=a+2/2sinαcosα  已知sin(α+β)sin(α－β)=1/3,求1/4sin²2α+sin²β+cos²αcos²α 已知sin(α+β)sin(α-β)=1/3求证1/4sin^2(2α)+sin^2β+cos^4α为定值 已知sin(α+β)*sin(α-β)=-1/3,求sin^2α-sin^2β的值 sin²1°+sin²2°+sin²3°+.+sin²89°= -1为什么? sin²1°+sin²2°+sin²3°……sin²89°=? sin²1°+sin²2°+sin²3°……sin²89°= 求sin²1°+sin²2°+sin²3°……sin²89°=? sin²1°+sin²2°+sin²3°.+sin²89°=