Question

представь в виде произведение sin14x+sin4x

Answer 1

sin(a+b) = sin(a)*cos(b)+sin(b)*cos(a),
sin(a-b) = sin(a)*cos(b) - sin(b)*cos(a),
sin(a+b) + sin(a-b) = 2*sin(a)*cos(b),
положим 
a+b = 14x,
a-b = 4x,
тогда
2a = 18x, a=9x,
2b = 10x, b =5x,
и
sin(14x)+sin(4x) = 2*sin(9x)*cos(5x).