2) You need pi because of the circumference to calculate how long the perimeter is. 3) 113.1 = Area 4) You would need to adjust how many number places of pi you use for how huge the number you need to calculate for. 5) To write an exact number for an irrational expression you need to calculate then round to the nearest hundredths after you get the number for either radius, diameter, or area. To find the approximate value you only use the minimum numbers such as 3.14 instead of 3.14159... 6) How this helped me better estimate the value of an irrational expression is by using more numbers for every extra number place the circle has in the diameter.
The other form of circle equation is (x-a)2 + (y-b)2 = r2. a and b is the coordinate of the center and r is radius. So the equation is x2+(y-4)2=9. Change it to the general form is x2+y2-8y+7=0. So A=1, B=1, C=0, D=-8 and E=7.
