Ответ:

ctg a^2

Объяснение:

1+cos 2a/2 / 1-cos 2a/2 = cos a^2/sin a^2 = (cos a/sin a)^2 = ctg a^2

1 - cos2a = sin^2x + cos^2x - ( cos^2x - sin^2x ) =

= sin^2x + cos^2x - cos^2x + sin^2x = 2sin^2x