Помогите решить, пожалуйста Log_2 tg П/8 + log_2 cos^2 П/8

log_2 [(tgπ/8)*(cos^2 (π/8)] = log_2 [(sin{π/8) /cos(π/8)] * [cos^2(π/8)] =  log_2 [(sin{π/8)*cos(π/8)]  log_2  (1/2)*2* [(sin{π/8)*cos(π/8)] =  log_2  [(1/2)*sin(2π/8)] = log_2(1/2)*sin(π/4) = log_2 (1/2)*(√2/2) = log_2[2^(-3/2)] = - 3/2