求實數(shù)a的取值范圍.求詳解,
求實數(shù)a的取值范圍.求詳解,
關(guān)于x的方程2cos^2x-sinx+a=0在[0,7π/6]上恰好有兩個不等實根,
關(guān)于x的方程2cos^2x-sinx+a=0在[0,7π/6]上恰好有兩個不等實根,
數(shù)學(xué)人氣：997 ℃時間：2020-08-31 08:16:12
優(yōu)質(zhì)解答
答案是（-17/8,-2].首先,把cos^2x化為1-sin^2x,得2sin^2x+sinx-a-2=0；再令t=sinx,得2t^2+t-a-2=0,由于x屬于[0,7π/6],畫出圖像,可以知道t屬于[-1/2,1]；令y=2t^2+t-a-2,圖像開口向上,且在點t=-1/2處的值為y(-1/2)=-...
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