Question

Докажите тождества! Заранее спасибо)

Answer 1

cos3b-(cos6b/sin6b)sin3b=cos3b-(cos^23b-sin^23b)sin3b/2sin3bcos3b=

=cos3b-(cos^23b-sin^23b)/2cos3b=(2cos^23b-cos^23b+sin^23b)/2cos3b=

=1/2cos3b