-2cos^2(x)-cosx+a+2=0
y=cosx, [-1,1]
-2y^2-y+a+2=0
a=2y^2+y-2
=2(y+1/4)^2-17/8
a1=-17/8, a2=1
a取值范围[-17/8, 1]
若关于x的方程-2cos^2(π+x)-cosx+a+2=0,求实数a的范围
若关于x的方程-2cos^2(π+x)-cosx+a+2=0,求实数a的范围
数学人气：969 ℃时间：2019-11-20 22:52:10
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