=cos^2x-1-acosx+1
=cos^2x-acosx
=(cosx-a/2)^2-(a^2)/4
當(dāng)a/2>=1時(shí),即a>=2,cosx=1時(shí),f(x)的最小值是1-a,所以1-a=-6,即a=7,
當(dāng)-2
綜上,滿足條件的a的值為7或-7
若f(x)=-sin^2x-acosx+1的最小值為-6,求2的值
若f(x)=-sin^2x-acosx+1的最小值為-6,求2的值
數(shù)學(xué)人氣：447 ℃時(shí)間：2020-09-12 22:04:05
優(yōu)質(zhì)解答
f(x)=-sin^2x-acosx+1
=cos^2x-1-acosx+1
=cos^2x-acosx
=(cosx-a/2)^2-(a^2)/4
當(dāng)a/2>=1時(shí),即a>=2,cosx=1時(shí),f(x)的最小值是1-a,所以1-a=-6,即a=7,
當(dāng)-2當(dāng)a<=-2時(shí),當(dāng)cosx=-1時(shí),f(x)取得最小值為1+a,所以1+a=-6,即a=-7,
綜上,滿足條件的a的值為7或-7
=cos^2x-1-acosx+1
=cos^2x-acosx
=(cosx-a/2)^2-(a^2)/4
當(dāng)a/2>=1時(shí),即a>=2,cosx=1時(shí),f(x)的最小值是1-a,所以1-a=-6,即a=7,
當(dāng)-2
綜上,滿足條件的a的值為7或-7
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