sin(3π/7)cos(π/14) + cos(3π/7)sin(π/14)
= sin(3π/7 + π/14)
= sin(6π/14 + π/14)
= sin(7π/14)
= sin(π/2)
= 1
sin(3π/7)cos(π/14) + cos(3π/7)sin(π/14)
= sin(3π/7 + π/14)
= sin(6π/14 + π/14)
= sin(7π/14)
= sin(π/2)
= 1