[toán 11]lượng giác

H

hn3

[TEX]sin^3x+sinx=cosx[/TEX]

[TEX]<=> sinx(sin^2x+1)=cosx[/TEX]

[TEX]==> sin^2x=cotx-1[/TEX]

[TEX]<=> \frac{1}{1+cot^2x}=cotx-1[/TEX]

Dễ rồi ;)
 
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