1. ## Is this possible?

Is it possible to prove a triangle ABC is isosceles, given only that Ậ = 50º

???????

thanks

2. Originally Posted by jacs
Is it possible to prove a triangle ABC is isosceles, given only that Ậ = 50º

???????

thanks

No. Since an isosceles triangle must have two equal angles, but the only
constraint on a general triangle is that the angle sum is 180 degrees.
So a triangle with an angle of 50 degrees could have its other angles as
60 and 70 degrees and hence need not be isosceles.

RonL

3. thanks for that, that is pretty much what i thought too, but teacher insists it can be done.

Should get his working tomorrow, which will prove interesting. I guess he must know some alternate universe geometry that we don't.

Or perhaps he just gave us the wrong info, (wouldnt be the first time)
lol

i will post his answer for a laugh, see what he manages to come up with

thanks CaptainBlack

4. how come the other two angles couldn't be 65 degrees?

5. Originally Posted by c_323_h
how come the other two angles couldn't be 65 degrees?
They could be, but you can't prove that they must be (at least not

RonL

6. Originally Posted by jacs
thanks for that, that is pretty much what i thought too, but teacher insists it can be done.

Should get his working tomorrow, which will prove interesting. I guess he must know some alternate universe geometry that we don't.

Or perhaps he just gave us the wrong info, (wouldnt be the first time)
lol

i will post his answer for a laugh, see what he manages to come up with

thanks CaptainBlack
Perhaps your teacher thinks in Lobachevskian Space?
(No idea how to spell it)

7. Originally Posted by ThePerfectHacker
Perhaps your teacher thinks in Lobachevskian Space?
(No idea how to spell it)
Still not a theorem in hyperbolic or elliptic geometries

RonL

8. Well, it turns out, ooopps surprise, he forgot a vital peice of information, like the second angle is also 50.

So that solves that little quandary, thanks for you input everyone.

jacs