March 20th, 2017, 11:42 PM  #1 
Newbie Joined: Mar 2017 From: USA Posts: 1 Thanks: 0  Area of circle
Does anybody know how to find the area of the larger circle knowing only that the radius of the smaller inner circles is equal to 5.2 ? thanks in advance,

March 21st, 2017, 12:55 AM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 2,427 Thanks: 1314 
draw a square connecting the centers of the smaller circles. It has side length $2r$ It's diagonal has length $d = 2\sqrt{2}r$ The diameter of the larger circle is $D = 2r + d = 2r(1+\sqrt{2})$ and it's radius $R = r(1+\sqrt{2})$ with area $A = \pi R^2 = \pi r^2(1+\sqrt{2})^2 = \pi r (3+2\sqrt{2})$ $A = (3+2\sqrt{3})\pi (5.2) = 30.3078 \pi$ 

Tags 
area, circle, trigonometry 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Finding the area of a circle inside a square only given the area of the square  skimanner  Math  12  July 8th, 2016 07:55 AM 
Perimeter and area of the circle  matemagia  Calculus  3  January 31st, 2015 05:39 AM 
Area enclosed by a semicircle and a quarter circle  yeoky  Algebra  4  May 3rd, 2014 01:06 AM 
Area of a Circle problem  Jamers328  Calculus  5  August 6th, 2012 01:02 PM 
Area of square with convex parts  area of circle  gus  Algebra  1  April 17th, 2011 04:25 PM 