A circle is centered at the origin with a radius of 5. Two lines are drawn that divide the circle into four regions, the first is the line y=1, and the other is x=3. Find the area of the largest region.
The largest region is of course the one containing the center/origin.
The arc measure in radians of this region is pi/2 + arcsin(3/5) + arcsin(1/5). The portion which is a sector of the circle therefore has area 25*(pi/2 + arcsin(3/5) + arcsin(1/5))/2.
There is also a right triangle with legs of lengths 1 and 5 and another with legs of lengths 3 and 5 as well as a 3x1 rectangle, adding 5/2 + 15/2 + 3 = 13 to the total.
The largest region therefore has area 25*(pi/2 + arcsin(3/5) + arcsin(1/5))/2 + 13 ~= 43.1956919547313
Correction, upon examining my work in regard to Steven Lord's comment:
The second right triangle does not have leg lengths of 3 and 5, but rather 3 and 4 (it's the hypotenuse that is length 5), to its area is 6, rather than 15/2. The area should be
25*(pi/2 + arcsin(3/5) + arcsin(1/5))/2 + 5/2 + 6 + 3 ~= 41.6956919547313
And now I see another error. The smaller right triangle's longer leg is not 5, but rather cos(arcsin(1/5)).
25*(pi/2 + arcsin(3/5) + arcsin(1/5))/2 + 5*cos(arcsin(1/5))/2 + 6 + 3 ~= 41.6451816975145
Edited on February 28, 2019, 3:33 pm

Posted by Charlie
on 20190227 15:09:30 