Sin 3 pi/14 - sin pi/14 - sin 5 pi /14 =

Question

Sin 3 pi/14 - sin pi/14 - sin 5 pi /14 =

Answer 1

Sin3π/14-(sinπ/14+sin5π/14)=sin3π/14-2sin3π/14cosπ87=sin3π/14(1-2cosπ/7)