Help? WILL MEDAL!

Question

Help? WILL MEDAL!

rz172 · Answer

attachment

rz172 · Answer

Is it 45 or  90?

rz172 · Answer

@SolomonZelman @harman.singh @caozeyuan

solomonzelman · Answer

We imply that BF and CE are parallel (and BF is not slanted relative to CE), given that B and F are midpoints of AC and AE (respectively).

solomonzelman · Answer

So, you know from there that the triangles (the whole triangle and the inner top triangle) are proportional.

solomonzelman · Answer

BF=90? I never said that, nor implied.

solomonzelman · Answer

Definitely not.

rz172 · Answer

But if they are parrallel?

rz172 · Answer

Does it mean it is 45 or am I wrong?

solomonzelman · Answer

Parallel doesn't mean equivalent length.

solomonzelman · Answer

You just before guessed 90, which was obvious incorrect, and now you say 45, so I hope you understand why, but I won't tell if you are correct about BF=45, unless you justify.

solomonzelman · Answer

How do you know BF=45 ?

solomonzelman · Answer

K, and how do you know that?

solomonzelman · Answer

I mean conceptually. What makes you think that BF has to be 1/2 of CE?

solomonzelman · Answer

I will do a restart and we will go a bit quicker.

rz172 · Answer

It's 45. Thanks for making it so much more complicated than it really is.

caozeyuan · Answer

you can prove the upper triangle is similiar to the larger one

solomonzelman · Answer

Next time I will not disrupt by over-complicating.
Bye:(