How did earth's atmosphere change during precambrian time?

The precambrian period was a time period that happened billions of years ago. Actually, 4.6 billion years, to be exact. The Earth started to form during this period. Layers of rock, elements of the land and waters, and many other things were developed during this time. The atmosphere had a mind of its own, per se, during this time period. It went through many different changes. The atmosphere went from being extremely cold and galactic to warming and having volcanoes, which allowed for an expansion of life forms.

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference.