P
pnhn2010


1) $cos2x- 2cos^3 x+sinx$=0
2) $sin^2 x=cos^2 x+ cos^2 3x$
:khi (15)::khi (15):
2) $sin^2 x=cos^2 x+ cos^2 3x$
:khi (15)::khi (15):
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