what is the formula for calculating the perimeter of a sector?
In these formulae r is the radius and d is the diameter. C = π X d (3.14159 x 10) = 31.42 (to 4 s. f.) To calculate the perimeter of an arc (part of a circle) from the angle you can calculate the fraction of the circle. = 4.19cm (to 3 s.f.) The perimeter of the whole sector is therefore 4.19 + 8 = 12.19 (4 s.f.).