There is a circle on svg, how to color it?

Question

JavaScript

There is radius = 57, there is stroke-dasharray = 358 (found by selection).
I'm not strong in mathematics, and I'm interested in how you can find the same value from formulas.

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" viewBox="0 0 200 200" preserveAspectRatio="none" class="progress">
<circle cx="100" cy="100" r="57" id="ac-c-bar" fill="none" stroke="#d1d1d1" stroke-width="2" stroke-dasharray="358, 358" transform="rotate(-90,100,100)"></circle>
<circle cx="100" cy="100" r="57" id="ac-c-progress" fill="none" stroke="#28aa6e" stroke-width="2" stroke-dasharray="358, 358" transform="rotate(-90,100,100)"></circle>
</svg>

Answer 1

2 * Pi * radius
Sandbox

Answer 2

fill="#ffff00"