y=cos^4x+sin^4x-3化成y=Asin(wx+f)的形式

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y=cos^4x+sin^4x-3化成y=Asin(wx+f)的形式

y=cos^4x+sin^4x-3化成y=Asin(wx+f)的形式
y=cos^4x+sin^4x-3化成y=Asin(wx+f)的形式

y=cos^4x+sin^4x-3化成y=Asin(wx+f)的形式
y=(sin^2x+cos^2x)^2-3-2sin^2xcos^2x=(cos4x-9)/4

切。。原来偷偷摸摸在知道上问。。我还以为你真知道呢
Y=4cos^4x+4sin^4x-3
=4cos^4x+4sin^4x+8cos^2x*sin^2x-8cos^2x*sin^2x-3
=4(cos^2x+sin^x)^2-8cos^2x*sin^2x-3
=1-8cos^2x*sin^2x
=1-2(sin2x)^2
=cos4x
=s...

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切。。原来偷偷摸摸在知道上问。。我还以为你真知道呢
Y=4cos^4x+4sin^4x-3
=4cos^4x+4sin^4x+8cos^2x*sin^2x-8cos^2x*sin^2x-3
=4(cos^2x+sin^x)^2-8cos^2x*sin^2x-3
=1-8cos^2x*sin^2x
=1-2(sin2x)^2
=cos4x
=sin(-4x+π/2)
Y<0就是
cos4x<0
2kπ+π/2<4x<2kπ+3π/2
kπ/2+π/8【虽然 这个也是我拷贝来的- -
我要分~~~~~~~~~~~~~~

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