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

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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 $C=2pir$ .

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

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