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Rut gon bthuc ;
[tex]B=sin^{2}\frac{\pi }{12}+sin^{2}\frac{3\pi }{12}+sin^{2}\frac{5\pi }{12}+sin^{2}\frac{7\pi }{12}+sin^{2}\frac{9\pi }{12}+sin^{2}\frac{11\pi }{12}[/tex]
[tex]C=cos^{2}\frac{\pi }{12}+cos^{2}\frac{3\pi }{12}+cos^{2}\frac{5\pi }{12}+cos^{2}\frac{7\pi }{12}+cos^{2}\frac{9\pi }{12}+cos^{2}\frac{11\pi }{12}[/tex]
[tex]B=sin^{2}\frac{\pi }{12}+sin^{2}\frac{3\pi }{12}+sin^{2}\frac{5\pi }{12}+sin^{2}\frac{7\pi }{12}+sin^{2}\frac{9\pi }{12}+sin^{2}\frac{11\pi }{12}[/tex]
[tex]C=cos^{2}\frac{\pi }{12}+cos^{2}\frac{3\pi }{12}+cos^{2}\frac{5\pi }{12}+cos^{2}\frac{7\pi }{12}+cos^{2}\frac{9\pi }{12}+cos^{2}\frac{11\pi }{12}[/tex]