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初等数学中求最值 ,一般思路都是通过等价变换 ,转化到只含一个变量时 ,才能求出它的最值 .如求ｆ(θ) =ｓｉｎ2 θ+3ｓｉｎθｃｏｓθ+4ｃｏｓ2 θ( 0≤θ≤ π2 )的最值 .我们通过三角变换 ,使它化为ｆ(θ) =3 22 ｓｉｎ( 2θ +π4) +52 来进行求解 .这里谈谈一般不能变为一
In elementary mathematics, the general idea is to convert to only one variable, and the general idea is to find its maximum value. For example, find f(θ) = sin2 θ + 3sinθcosθ + 4cos2 θ ( 0 ≤ θ The maximum value of ≤ π2 ). We transform it by trigonometric transformation to f(θ) = 3 22 sin( 2θ + π4) +52. We can’t change it here.