sin (0,5П+а)+cos (П-за)/1-cos (-2a)

(sin (π/2 + α) + cos (π - 3α))/(1 - cos (-2α)) = (cos α - cos 3α)/(1 - cos 2α) = 2sin α·sin 2α/2sin²α = 4sin²α·cosα/2sin²α = 2cos α