1.6 KiB
1.6 KiB
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5900f4ee1000cf542c510000 | Problem 385: Ellipses inside triangles | 5 | 302049 | problem-385-ellipses-inside-triangles |
--description--
For any triangle T
in the plane, it can be shown that there is a unique ellipse with largest area that is completely inside T
.
For a given n
, consider triangles T
such that:
- the vertices of
T
have integer coordinates with absolute value≤ n
, and - the foci1 of the largest-area ellipse inside
T
are(\sqrt{13}, 0)
and(-\sqrt{13}, 0)
.
Let A(n)
be the sum of the areas of all such triangles.
For example, if n = 8
, there are two such triangles. Their vertices are (-4,-3), (-4,3), (8,0) and (4,3), (4,-3), (-8,0), and the area of each triangle is 36. Thus A(8) = 36 + 36 = 72
.
It can be verified that A(10) = 252
, A(100) = 34\\,632
and A(1000) = 3\\,529\\,008
.
Find A(1\\,000\\,000\\,000)
.
1The foci (plural of focus) of an ellipse are two points A
and B
such that for every point P
on the boundary of the ellipse, AP + PB
is constant.
--hints--
ellipsesInsideTriangles()
should return 3776957309612154000
.
assert.strictEqual(ellipsesInsideTriangles(), 3776957309612154000);
--seed--
--seed-contents--
function ellipsesInsideTriangles() {
return true;
}
ellipsesInsideTriangles();
--solutions--
// solution required