Toán Lớp 11: help!!
\[{\cos ^2} – \sin x\,\cos x = 0\]
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Toán Lớp 11: help!!
\[{\cos ^2} – \sin x\,\cos x = 0\]
Comments ( 2 )
<=> cosx(cosx – sinx) = 0
<=> cosx = 0 <=> x = π/2 + kπ , k thuộc Z
hoặc cosx – sinx = 0
<=> cosx = sinx
<=> sinx = sin(π/2 – x)
<=> x = π/2 – x + k2π<=> x = π/4 + kπ , k thuộc Z
hoặc x = π – π/2 + x +k2π
<=> x = π/2 + k2π , k thuộc Z (vô lí)
vậy ….