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thong1990nd
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1) tính
[TEX]a/ sin18^{o}[/TEX]
[TEX]b/sin15^{o}[/TEX]
[TEX]c/Cos{\frac{\pi}{8}}[/TEX],
[TEX]d/ Cos{\frac{5\pi}{8}}[/TEX]
2)
a) tính [TEX]A=cos20.cos40.cos60.cos80[/TEX]
b) [TEX]B=[/TEX]cos[TEX]\frac{\pi}{7}[/TEX].cos[TEX]\frac{4\pi}{7}[/TEX].cos[TEX]\frac{5\pi}{7}[/TEX]
c) [TEX]C= sin10.sin20.sin40[/TEX]
3) tính [TEX]A=[/TEX]cos[TEX]\frac{\pi}{5}[/TEX].cos[TEX]\frac{2\pi}{5}[/TEX]
Áp dụng tính [TEX]B=sin{\frac{\pi}{5}}.sin{\frac{2\pi}{5}}.sin{\frac{3\pi}{5}}.sin{\frac{4\pi}{5}}[/TEX]
4) tính [TEX]tan37,5^{o}[/TEX]
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[TEX]a/ sin18^{o}[/TEX]
[TEX]b/sin15^{o}[/TEX]
[TEX]c/Cos{\frac{\pi}{8}}[/TEX],
[TEX]d/ Cos{\frac{5\pi}{8}}[/TEX]
2)
a) tính [TEX]A=cos20.cos40.cos60.cos80[/TEX]
b) [TEX]B=[/TEX]cos[TEX]\frac{\pi}{7}[/TEX].cos[TEX]\frac{4\pi}{7}[/TEX].cos[TEX]\frac{5\pi}{7}[/TEX]
c) [TEX]C= sin10.sin20.sin40[/TEX]
3) tính [TEX]A=[/TEX]cos[TEX]\frac{\pi}{5}[/TEX].cos[TEX]\frac{2\pi}{5}[/TEX]
Áp dụng tính [TEX]B=sin{\frac{\pi}{5}}.sin{\frac{2\pi}{5}}.sin{\frac{3\pi}{5}}.sin{\frac{4\pi}{5}}[/TEX]
4) tính [TEX]tan37,5^{o}[/TEX]
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