Question

4cos2π\7cosπ\7-2cos2π\7

Answer 1

solution is-:
4cos(2p/7) cos(p/7)-1=1.24

2cos (2p/7)=1.24

Answer 2

Cos2π =1, cosπ =-1
→4/-7/7-2/7= 4/-7/5/7
→4/-7 × 7/5=4/-49/5
→4×5/-49=-20/49