[Toán 10] Bài tập lượng giác

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myrainbow210

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wagashi.13

$ \frac{cos2x-sin4x-cos6x}{cos2x+sin4x-cos6x}=\frac{2sin2x-1}{2sin2x+1} $

$tan(x-15)cot(x+15)=\frac{sin(x-15)}{cos(x-15)}.\frac{cos(x+15)}{sin(x+15)}=\frac{\frac{1}{2}(sin2x-sin30)}{\frac{1}{2}(sin2x+sin30)}= \frac{2sin2x-1}{2sin2x+1} \rightarrow dpcm$
 
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