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sin3x Cos3x

sin3a=3sina-4sinacos3a =4cosa-3cosa 推导方法如下:sin3a=sin(2a+a)=sin2a*cosa+cos2a*sina=2*sina*cosa*cosa+(1-2sina)*sina=2sina*(1-sina)+(1-2sina)*sina=2sina*(1-sina)+(1-2sina)*sina=2sina-2sina+sina-2sina=

sin3x=3sinx-4(sinx)^3 cos3x=4(cosx)^3-3cosx

3sin3x+cos3x=03sin3x=-cos3x tan3x=-1/3 3x=arctan(-1/3)+kπ x=[arctan(-1/3)+kπ]/3 希望你能看懂,你能明白, 望采纳,赞同

sin3x+cos3x=√2(√2/2*sin3x+√2/2cos3x)=√2(sin3xcosπ/4+cos3xsinπ/4)=√2sin(3x+π/4)

解:sin3xcos3x=1/2sin6x

y=sin3x cos3x=0.5sin6x=0.5cos(π/2-6x)=0.5cos(6x-π/2)=0.5cos(6(x-π/12))所以相当于把y=sin3x cos3x的图像向右平移π/12个单位

√2/2y=√2/2sinx+√2/2cosx √2/2y=cos(π/4)sinx+sin(π/4)cosx √2/2y=sin(x+π/4) y= √2sin(x+π/4),做下参考吧 再看看别人怎么说的.

y=Sin3x-Sin(π/2-3x) =2Cos[(3x+π/2-3x)/2]Sin[(3x+π/2+3x)/2] =2Cos(π/4)Sin(3x+π/4) =√2Sin(3x+π/4) 所以最大值是√2 当且仅当3x+π/4=2kπ+(π/2)时取到,(k=1,2,3,……) 此时x=(2/3)kπ+(π/12),(k=1,2,3,……)

y=sin3x+cos3x=√2(√2/2sin3x+√2/2cos3x)=√2sin(3x+π/4)那么-√2≤y≤√2所以y的最大值为√2,最小值为-√2

正负根号2.

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