Question

докажите тождество 1)(sin t)*(ctg t) = cos t

2)((sin t)/(tg t))= cos t

3)(cos t)*(tg t)=sin t

4)((cos t)/(ctg t))=sin t

Answer 1

1)sin t · ctg t = cos t

   sin t · cost / sint) = cos t

   cost ≡ cos t

2) sin t / tg t = cos t

   sin t /( sint/cost) = cos t

   sin t ·cost/ sint = cos t

   cost ≡ cos t

3)cost · tgt = sin t

   cost · sint/cost = sin t

   sint ≡ sint

4)cos t / ctg t = sin t

  cos t /(cost/sint) = sin t

   cos t·sint /cost = sin t

   sint ≡ sint