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.
(In reply to
solution  math and computer by Steven Lord)
Going back to my comment, I see I did make a mistake: I used the length of the hypotenuse as the length of one of the legs of one of the right triangles. But I was not using the right triangles to approximate half sections.
The triangle with that error was the one from (0,0) to (3,0) to (3,4), partially filling in what's not covered by the large sector from central angle arcsin(1/5) to pi/2+arcsin(3/5).
I see my further error now, that I'm thinking about it: the leg of the skinnier triangle at the lower right is also not 5; it's 5*cos(arcsin(1/5)). Now it agrees with your answer, and I have modified my post a second time.

Posted by Charlie
on 20190228 15:33:07 