How do you find the circumference of the circle #x^2 + y^2 = 28#?

Question

5558 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-01-04T22:20:20

#4pisqrt7#

This is an equation for a circle in standard form:

#(x-h)^2+(y-k)^2=r^2#

We'll only concern ourselves with the radius #r# since we want to find the circle's circumference.

From the equation, we know that #r^2=28#. Thus, #r=sqrt28#.

This can be simplified since #sqrt28=sqrt4sqrt7=2sqrt7#.

If #r=2sqrt7#, we can find the circumference through the formula #C=2pir#.

#C=2pi(2sqrt7)=4pisqrt7#