f(x)=4sin(2x+π/3 ) 可以改写为f(x)=4cos(2x-π/6),为什么

函数f(x)=(x-x^2)/sinπx的可去间断点个数/> 证明f(x)=sgn(sinπ/x)可积 求导f(x) = 4x^3 + sin(x^2) 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 f(x)=cos(2x-x/3)+2sin(x-π/4)sin(x+π/4)sin(x+π/4)化简. 一个关于导数的疑惑f(x)=(sinx-cosx)/x=√2sin(x-π/4)/x,导数f'(x)=(cos(x-π/4)x-sin(x-π/4))/x^2,x∈（π/4,3π/4）,此时cos(x-π/4),sin(x-π/4)都为正数,那么x=tan(x-π/4)不应该是f(x)的极小值吗.可为什么答案是极大 f(x)=2sin^2(π/4+x)+根号3(sin^2x+cos^2x)f(x)=2sin^2(π/4+x)+根号3(sin^2x-cos^2x) 符号打错了 设f(x)可微.y=f(lnx)+f(sin^2*x),求dy f(x)=2sin(π/4 x+π/4) 计算f(1)+f(2)+f(3)+...f(2011) 说出f(x)=2sin(2x-π/3)可由y=cosx作出怎样的变化得到 函数f（x）=sin(2x+π/3）图像的对称轴方程可以为 f(x)=（1+cotx)sin^2x-2sin(x+π/4)sin(x-π/4)还有一题, 已知函数f(x)=(1+1 anx)sin^2x+m sin(x+π/4)sin(x-π/4) 设f(x)可导,求下列函数的导数(1)y=f(2x+1)(2)y=[xf(x^2)]^2(3)y=f(e^x)*e^f(x)(4)y=f(sin^2 x)+f(cos^2 x),求y'|x=π/4 f(x)=sin(x+π/4)图像怎样变成F(x)=cos(2x) f(x)=2sinx*sin(x+π/3) 化简 函数f(x)=2sin(x+π/4)sin(x-π/4)+sin2x的值域 求f【x】=2sin[x+π/4]sin[x-π/4]+sin2x的最大值