数学 8sin^2 x - 10cosx - 11 = 0??
来源:百度知道 编辑:UC知道 时间:2024/06/01 04:14:00
0≤x≤2pi
8sin^2 x - 10cosx - 11 = 0??
8sin^2 x - 10cosx - 11 = 0??
8sin^2 x - 10cosx - 11 = 0
8-8cos^2 x - 10cosx - 11 = 0
8cos^2 x + 10cosx +3 =0
(2cosx+1)(4cosx+3)=0
所以,cosx=-1/2或-3/4。
由cosx=-1/2得x=2π/3或x=4π/3;
由cosx=-3/4得x=π-arccos 3/4或x=π+arccos 3/4
所以,x=2π/3 或 x=4π/3,或 x=π-arccos 3/4,或 x=π+arccos 3/4
-8Cos^2x-10Cosx-3=0
Cosx=-1/2或Cosx=-3/4
所以x=1/3pi或2/3pi或arcCos(-3/4)或pi-arcCos(-3/4)
数学 8sin^2 x - 10cosx - 11 = 0??
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