Asymbol on a compass or map that is circular with graded points for the direction is commonly known as a
a) grid system
b)scale
c)legend
d)compass rose

AnswerD) Compass roseExplanation:

A Compass Rose is the one that shows the directions on a Map which involves the Cardinal directions such as north, south, east, and west as well as the Intermediate directions such as northeast, southeast, southwest, and northwest. Sometimes, It is also called as a wind-rose or Rose of the Winds. So we can say that symbol on a compass or map that is circular with graded points for the direction is commonly are known as the compass rose

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.