Phuong trinh luong giac?
Phuong trinh luong giac?
ptlgiac :2cos3x-2co2x+2cosx=1
=> 2(cos3x+cosx)-2cos2x
=>2.2cos2x.cosx-2cos2x=1
=>4cos2x.cosx-2cos2x-1=0
=>4(2cos2x-1)cosx-2(2cos2x-1)-1=0
=>8cos3-4cos2x-4cosx+1=o
tới đây tự bấm máy tính nha.
Trang Trước
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