Answer:
OA.True
Step-by-step explanation:
is true
bcos if u multply sin(x/7)sin(x/7) u will have
sin²(x/7)
from trigonometry identity
sin²(x/7)+cos²(x/7)=1
sin²(x/7)=1-cos²(x/7)...............(1)
from trigonometry identity
cos(2x/7)=cos²(x/7) - sin²(x/7)
cos²(x/7)=cos(2x/7)+sin²(x/7) ........(2)
subtitue (2) in (1) we have
sin²(x/7)=1-(cos(2x/7)+sin²(x/7))
=1-cos(2x/7) - sin²(x/7)
sin²(x/7)+sin²(x/7)=1-cos(2x/7)
2sin²(x/7)=1-cos(2x/7)
sin²(x/7)=½(1-cos(2x/7)
sin(x/7)sin(x/7)=½(1-cos(2x/7))
