Thread: Is this possible?

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

???????


thanks

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

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

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

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
without some additional conditions).

RonL

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)

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

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