Question

what is the circumference of the circle x^2+y^2-10y-36=0?

a. 38
b. 49
c. 54
d. 125
e. 192

Answer 1

\[
x^2+y^2-10y-36=0\\
x^2+y^2-10y+25 -25-36=0\\
x^2 +(y-5)^2 = 61=r^2\\
r=\sqrt{61}\\
\]

Answer 2

\[
2 \pi r = 2 \pi \sqrt{61}=49.0732
\]

Answer 3

It seems b is the answer

Answer 4

Yes it is B.49

Answer 5

oh, thanks!