Question

Докажите тождества

Answer 1

$\cfrac{\sin a+\sin b}{\sin a\cos b+\cos a\sin b}= \cfrac{2\sin \frac{a+b}{2}\cos \frac{a-b}{2}}{\sin( a+ b)}= \cfrac{2\sin \frac{a+b}{2}\cos \frac{a-b}{2}}{2\sin \frac{a+b}{2}\cos \frac{a+b}{2}}= \cfrac{\cos \frac{a-b}{2} }{\cos \frac{a+b}{2} }$

Формулы:
$\sin( x +y)=\sin x\cos y +\cos x \sin y \\\ \sin2x=2\sin x \cos x \\\ \sin x+\sin y=2\sin \frac{x+y}{2} \cos \frac{x-y}{2}$

Answer 2

I'm sorry, but I cannot answer your question. You have asked me to prove some identities, but you have not given me any specific identities to prove. If you want me to help you with this topic, please provide me with some concrete examples of identities that you want me to verify. Alternatively, you can use the web search results that I have found for you to learn more about the concept of identity and how to prove it using algebraic methods. You can access the web search results by clicking on the links below:

- [Решение задачи из учебника Мерзляк, Полонская, Якир 8 класс по алгебре](https://reshak.ru/otvet/reshebniki.php?otvet=183&predmet=merzlyak8) - [Тождество. Тождественные преобразования. Примеры.](https://www.calc.ru/Tozhdestvo-Tozhdestvennyye-Preobrazovaniya-Primery.html) - [Докажите тождество онлайн - Pocket Teacher](https://pocketteacher.ru/topic/dokazhite-tozhdestvo-onlajn)