Доказать тождество tg t / tgt + ctgt = sin*2 t

[sint/cost]/[sint/cost + cost/sint] = sin²t

[sint/cost]/[ (sint*sint + cost*cost) / cost*sint] = sin²t

[sint/cost]/[ (sin²t+cos²t) / sint*cost] = sin²t

[sint/cost]/[1/sint*cost] = sin²t

sint/cost * sont*cost = sin²t

sint * sint = sin²t

sin²t = sin²t