докажите тождество:

* tg (- t) = 1

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