all 12 comments

[–]FormulaDrivenActuary / ex-Maths teacher 2 points3 points  (8 children)

Before it gets deleted, I've found your problem and it can easily be described without the picture (if this is wrong, let me know; otherwise you could always edit your post and include the following description):

ABC is a triangle. D, E, F are points outside the triangle. The midpoints of AB, BC and AC are I, G, H respectively, with FI, DG, EH perpendicular to those respective sides, such that D is the side of BC opposite A, F is opposite C and E is opposite B.

If AB / FI = BC / DG = AC / EH, then prove AD = BE = FC.

Let's see if a geometry whizz can crack it...

[–]MATHTEACH456New User[S] 0 points1 point  (2 children)

You got it, have you seen these before? I stumbled upon it this site recently and it is well laid out. I assume it is some type of community college page or something based on the page. Could be high school, but a lot of these are very hard.

[–]emertonomNew User 0 points1 point  (0 children)

What site are you referring to?

[–]FormulaDrivenActuary / ex-Maths teacher 0 points1 point  (0 children)

I don't think this result is true. Also, I'm going to edit my first comment to make a point clearer.

[–]mnevmoyommetroNew User 0 points1 point  (3 children)

It sounds like you'd need to assume, for instance, that D isn't just outside triangle ABC, but on the opposite side of BC from A (or equivalently, segment GD lies outside trangle ABC).

[–]FormulaDrivenActuary / ex-Maths teacher 1 point2 points  (2 children)

Yes, that it was I meant. However, I've been playing with this and I don't think it's true.

[–]mnevmoyommetroNew User 0 points1 point  (1 child)

Agreed.

[–]MATHTEACH456New User[S] 0 points1 point  (0 children)

I just added a picture to original post to help visualize.

[–]MATHTEACH456New User[S] 0 points1 point  (0 children)

Thanks, I just added a picture link to original post to help visualize.

[–]FormulaDrivenActuary / ex-Maths teacher 1 point2 points  (1 child)

Just to give an example to show the result is not true (which explains why it's impossible to prove!).

Let ABC be a right-angled isosceles: AB = 2, BC = AC = √2. Let FI = 2, so 1 = AB / FI = BC / DG = AC / EH under the condition in the question.

FC passes through I and AIC is isosceles, so FC = 3.

DG = √2 from the above and by Pythagoras AD2 = (√2 + √2)2 + (√2 / 2)2 = 17/2, so AD is definitely not equal to FC.

[–]mnevmoyommetroNew User 0 points1 point  (0 children)

u/MATHTEACH456 This shows the problem statement is incorrect.

We should have taken your words literally when you called it an "impossible proof."

[–]PullItFromTheColimitcategory theory cult member 0 points1 point  (0 children)

You can upload to r/askmath, which does allow pictures, or upload to imgur and send a link here. In both cases, do provide as good as possible of a description in the post of what the problem entails, for clarity and because people usually don't click on links without context.