докажите тождество: sina+ sin3a+ sin5a/ cosa+ cos3a+cos5a =tg3a. ребят помогите а.

sin4a + sin5a + sin6a = sin4a + sin6a + sin5a , 2sin(5a)*cosa + sin5a = sin5a(2cosa+1)cos4a + cos5a + cos6a = cos4a + cos6a + cos5a , 2cos5a*cosa + cos5a = cos5a(2cosa+1)sin5a(2cosa+1)/cos5a(2cosa+1) = sin5a/cos5a = tg5a

(sina+sin3a+sin5a)/(cosa+cos3a+cos5a)=(2sin3acos2a+sin3a)/(2cos3acos2a+cos3a)= =(sin3a(2cos2a+1))/(cos3a(2cos2a+1))=tg3aа где остальные?