[Toán 11] Lượng giác

H

huy266

[tex]4\sin ^{3}x\cos 3x=4\sin ^{3}x(4\cos ^{3}x-3\cos x)[/tex]
[tex]4\cos ^{3}x\sin 3x= 4\cos ^{3}x(3\sin x-4\sin ^{3}x)[/tex]
[tex]12\sin x\cos ^{3}x-12\cos x\sin ^{3}x=6\sin 2x\cos 2x=3\sin 4x[/tex]
đến đây ok rồi
 
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