（2√3）sinB+（2√3）sin(2π/3 -B)
=2√3(sinB+sin(2π/3 -B))
=2√3(sinB-sin(-π/3-B))
=2√3(sinB+sin(π/3+B))
=2√3(sinB+sinπ/3cosB+cosπ/3sinB)
=2√3(sinB+√3/2cosB+1/2sinB)
=2√3(3/2sinB+√3/2cosB)
=3cosB+(3√3)sinB