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
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