а) tg(α)^2 + sin(α)^2 - 1/cos(α)^2 = sin(α)^2 - 1 = -cos(α)^2
б) cos(3α) + cos(α)/2cosα + 2sin(α)^2 = 2cos(2α)cos(α)/2cos(α) + 1 - cos(2α) =
cos(2α) + 1 - cos(2α) = 1
