Question

  решите пожалуйста 
sin 4a/cos3a+cosa

Answer 1

$frac{sin4 alpha }{cos3 alpha +cos alpha }= frac{2sin2 alpha *cos2 alpha }{2cos( frac{3 alpha + alpha }{2})*cos( frac{3 alpha - alpha }{2}) } = frac{2sin2 alpha *cos2 alpha }{2cos2 alpha *cos alpha }$ = $frac{sin2 alpha }{ cos alpha }= frac{2sin alpha *cos alpha }{cos alpha } =2sin alpha$