ai giúp mình gấp mài thi rồi?

T

tranvanhung7997

2/ sin$^2$x + cos$^2$2x + sin$^2$3x = 1
<=> 2sin$^2$x + 2cos$^2$2x + 2sin$^2$3x = 2
<=> 2cos$^2$2x = 1 - 2sin$^2$x + 1 - 2sin$^2$3x
<=> 2cos$^2$2x = cos2x + cos6x
<=> 2cos$^2$2x = 2. cos4x. cos2x
<=> cos2x.(cos2x - cos4x) = 0
<=> 2.cos2x.sin3x.sinx = 0
..............
 
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