от ева » 31 Май 2018, 03:33
[tex]\frac{2sin\alpha-sin2\alpha}{2sin\alpha+sin2\alpha}[/tex]=
=[tex]\frac{2sin\alpha-2sin\alpha.cos\alpha}{2sin\alpha+2sin\alpha.cos\alpha}[/tex]=
=[tex]\frac{2sin\alpha(1-cos\alpha)}{2sin\alpha(1+cos\alpha)}[/tex]=
=[tex]\frac{2sin^{2}\frac{\alpha}{2}}{2cos^{2}\frac{\alpha}{2}}[/tex]=
=[tex]tg^{2}[/tex][tex]\frac{\alpha}{2}[/tex]