Sin²d-sin²d*cos²d=sin²d*(1-cos²d)=sin²d*sin²d=sin⁴d.
1) 1 - cos2t + sin2t = cos^2t + sin^2t - cos^2t + sin^2t +2sintcost =
= 2sin^2t + 2sintcost = 2sint(sint + cost)
2) 1 + cos2t + sin2t = cos^2t + sin^2t + cos^2t - sin^2t +2sintcost =
= 2cos^2t + 2sintcost = 2cost(cost + sint)
3) tg(П/2 - t) = ctgt
4) 2sint(sint + cost)*ctgt/[2cost(cost + sint)] = tgt*ctgt = 1