The appropriate formula is C = 2*pi*r.
Here, C = 2*pi*(50 units) = 100*pi units (answer)
As per the isosceles triangle theorem, if the two base angles are congruent then the legs are also congruent, so we must set the two legs equal to each other:
2z - 15 = 9
Add 15 to both sides:
15 - 15 = 0
15 + 9 = 24
Divide 2 from each side:
2z = 24
2z/2 = z
24/2 = 12
z = 12
Hence, the answer would be D: z = 12
