Question 1165291
r = 7cm
ϴ=120°=(120°)(2π/360)=2π/3
Do you mean the length of the arc as the perimeter?
 
s (length of the arc) = ϴ*r

s=rϴ
s=(7) (2π/3) 
s=14π/3=14.66cm

Hope that helps!