ПОМОГИТЕ ПОЖАЛУЙСТА!!!
Вычислите:
sin2a,cos2a и tg 2a:
tga=-3/4 и п/2 < a <п
Ответ должен получиться : -24/25, 7/25, - 24/7
Ответы на вопрос
Ответил Apofeoz
0
В промежутке 
имеет знак ![[/tex], а [tex]sin2 alpha , tg2 alpha](https://tex.z-dn.net/?f=%5B%2Ftex%5D%2C+%D0%B0+%5Btex%5Dsin2+alpha+%2C+tg2+alpha+ "[/tex], а [tex]sin2 alpha , tg2 alpha")
— знак ![[/tex] (Обратите внимание: это функции двойного аргумента!)<br><br></span>[tex]tgalpha=-frac{3}{4}\\sin2 alpha =frac{2tg alpha }{1+tg^2 alpha },\sin2 alpha
=frac{2bullet(-frac{3}{4})}{1+(-frac{3}{4})^2}=frac{-frac{6}{4}}{1+frac{9}{16}}=-frac{3}{2+frac{9}{8}}=-frac{3}{frac{25}{8}}=-frac{24}{25};\\cos2
alpha =+sqrt{1-sin^22 alpha },\cos2 alpha
=sqrt{1-(-frac{24}{25})^2}=sqrt{1-frac{576}{625}}=sqrt{frac{49}{625}}=frac{7}{25};\\tg2
alpha =frac{sin2 alpha }{cos2 alpha },\\tg2 alpha
=frac{-frac{24}{25}}{frac{7}{25}}=-frac{24}{7}.](https://tex.z-dn.net/?f=%5B%2Ftex%5D+%28%D0%9E%D0%B1%D1%80%D0%B0%D1%82%D0%B8%D1%82%D0%B5+%D0%B2%D0%BD%D0%B8%D0%BC%D0%B0%D0%BD%D0%B8%D0%B5%3A+%D1%8D%D1%82%D0%BE+%D1%84%D1%83%D0%BD%D0%BA%D1%86%D0%B8%D0%B8+%D0%B4%D0%B2%D0%BE%D0%B9%D0%BD%D0%BE%D0%B3%D0%BE+%D0%B0%D1%80%D0%B3%D1%83%D0%BC%D0%B5%D0%BD%D1%82%D0%B0%21%29%3Cbr%3E%3Cbr%3E%3C%2Fspan%3E%5Btex%5Dtgalpha%3D-frac%7B3%7D%7B4%7D%5C%5Csin2+alpha+%3Dfrac%7B2tg+alpha+%7D%7B1%2Btg%5E2+alpha+%7D%2C%5Csin2+alpha+%0A%3Dfrac%7B2bullet%28-frac%7B3%7D%7B4%7D%29%7D%7B1%2B%28-frac%7B3%7D%7B4%7D%29%5E2%7D%3Dfrac%7B-frac%7B6%7D%7B4%7D%7D%7B1%2Bfrac%7B9%7D%7B16%7D%7D%3D-frac%7B3%7D%7B2%2Bfrac%7B9%7D%7B8%7D%7D%3D-frac%7B3%7D%7Bfrac%7B25%7D%7B8%7D%7D%3D-frac%7B24%7D%7B25%7D%3B%5C%5Ccos2%0A+alpha+%3D%2Bsqrt%7B1-sin%5E22+alpha+%7D%2C%5Ccos2+alpha+%0A%3Dsqrt%7B1-%28-frac%7B24%7D%7B25%7D%29%5E2%7D%3Dsqrt%7B1-frac%7B576%7D%7B625%7D%7D%3Dsqrt%7Bfrac%7B49%7D%7B625%7D%7D%3Dfrac%7B7%7D%7B25%7D%3B%5C%5Ctg2%0A+alpha+%3Dfrac%7Bsin2+alpha+%7D%7Bcos2+alpha+%7D%2C%5C%5Ctg2+alpha+%0A%3Dfrac%7B-frac%7B24%7D%7B25%7D%7D%7Bfrac%7B7%7D%7B25%7D%7D%3D-frac%7B24%7D%7B7%7D. "[/tex] (Обратите внимание: это функции двойного аргумента!)<br><br></span>[tex]tgalpha=-frac{3}{4}\\sin2 alpha =frac{2tg alpha }{1+tg^2 alpha },\sin2 alpha
=frac{2bullet(-frac{3}{4})}{1+(-frac{3}{4})^2}=frac{-frac{6}{4}}{1+frac{9}{16}}=-frac{3}{2+frac{9}{8}}=-frac{3}{frac{25}{8}}=-frac{24}{25};\\cos2
alpha =+sqrt{1-sin^22 alpha },\cos2 alpha
=sqrt{1-(-frac{24}{25})^2}=sqrt{1-frac{576}{625}}=sqrt{frac{49}{625}}=frac{7}{25};\\tg2
alpha =frac{sin2 alpha }{cos2 alpha },\\tg2 alpha
=frac{-frac{24}{25}}{frac{7}{25}}=-frac{24}{7}.")
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