Question

Докажите тождество 2cos^2 a tg a/sin^2 a-cos^2 a=-tg 2 a?

Answer 1

1.sin(  )  sin cos  cos sin  .2.cos(  )  cos cos  sin sin  .3.   1 tg tgtg tg tg( )  )2,2,2( n n m           .4.   ctg ctgctg ctg 1ctg( ) , (  n,   n,     m