Докажите тождество cos(5π/2 − 6a) + sin(π + 4a) + sin(3π − a) / (sin(5π/2 + 6a) + cos(4a − 2π) + cos(a + 2π)) = tga

cos(5π/2 − 6a) = sin 6a. sin(π + 4a) = -sin 4a. sin(3π − a) = sin a. sin(5π/2 + 6a) = cos 6a. cos(4a − 2π) = cos 4a. cos(a + 2π) = cos a. (sin 6a - sin 4a + sin a) / (cos 6a + cos 4a + cos a) = tga. Доказано.