Question

someone please explain me how sin 4π/7 became sin 3π/7 in this step.​

Answer 1

sin(4π/7)=sin(π-3π/7)

:. sin(π-theeta)=sintheeta

=sin3π/7

Answer 2

$\sin(3\pi \div 7 ) - \sin(\pi \div 7) as \sin(\pi - 4\pi \div 7 ) = \sin(3\pi \div 7 \\ )$