[[toán 10] lượng giác

C

cuncon2395

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T

thaivanphat_1995

C=[tex]sin^4.\frac{\pi}{16}+sin^4.\frac{3\pi}{16}+ cos^4.\frac{3\pi}{16}+cos^4.\frac{\pi}{16}[/tex]
=[tex]1-2sin^2\frac{\pi}{16}.cos^2\frac{\pi}{16}+1-2sin^2\frac{3\pi}{16}.cos^2\frac{3\pi}{16}[/tex]
=[tex]2-\frac{sin^2.\frac{\pi}{4}}{2}-\frac{sin^2.\frac{3\pi}{4}}{2}[/tex]
còn lại bấm máy tính :p
 
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