If two angles of a triangle are equal, is the triangle : Quant Question Archive [LOCKED]
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 23 Jan 2017, 14:04

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If two angles of a triangle are equal, is the triangle

Author Message
Director
Joined: 20 Sep 2006
Posts: 658
Followers: 2

Kudos [?]: 111 [0], given: 7

If two angles of a triangle are equal, is the triangle [#permalink]

### Show Tags

30 Jul 2008, 17:14
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If two angles of a triangle are equal, is the triangle isosceles???

My answer is no. Because we dont knwo the thrid angle. And if the thrid angle is same too then its an equilateral triangle.

Is that true?
Director
Joined: 10 Sep 2007
Posts: 947
Followers: 8

Kudos [?]: 287 [0], given: 0

### Show Tags

30 Jul 2008, 17:21
I think answer should be yes. Even an equilateral triangle is an special case of Isoceles triangle in which third angle happens of to be same as the other two triangles.

It is the same logic as why every square is rhombus or rectangle.
GMAT Tutor
Joined: 24 Jun 2008
Posts: 1183
Followers: 422

Kudos [?]: 1510 [0], given: 4

### Show Tags

30 Jul 2008, 17:54
I don't think there's a universally accepted answer to this question in math circles. It is now normal to consider equilateral triangles as isosceles (just as squares are considered parallelograms), but that wasn't always the case- two or three hundred years ago, an isosceles triangle was normally defined to have precisely two equal sides and angles - and I'd bet there are still people who go by that definition. This is not a distinction you will ever need to know about for the GMAT, but if you're curious, the Official Guide defines an isosceles triangle as one with 'at least two equal sides', so equilateral triangles are officially isosceles on the GMAT.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Director
Joined: 20 Sep 2006
Posts: 658
Followers: 2

Kudos [?]: 111 [0], given: 7

### Show Tags

30 Jul 2008, 18:15
IanStewart wrote:
I don't think there's a universally accepted answer to this question in math circles. It is now normal to consider equilateral triangles as isosceles (just as squares are considered parallelograms), but that wasn't always the case- two or three hundred years ago, an isosceles triangle was normally defined to have precisely two equal sides and angles - and I'd bet there are still people who go by that definition. This is not a distinction you will ever need to know about for the GMAT, but if you're curious, the Official Guide defines an isosceles triangle as one with 'at least two equal sides', so equilateral triangles are officially isosceles on the GMAT.

Thanks for pointing out. Make sense now....
SVP
Joined: 29 Aug 2007
Posts: 2492
Followers: 68

Kudos [?]: 736 [0], given: 19

### Show Tags

30 Jul 2008, 21:03
rao_1857 wrote:
If two angles of a triangle are equal, is the triangle isosceles???

My answer is no. Because we dont knwo the thrid angle. And if the thrid angle is same too then its an equilateral triangle.

Is that true?

its an interesting but i think it is. the question is similar to is 64 a square of an integer? yes, it is. since 64 is a cube of 4, it doesnot mean that its not a square. its a square and a cube as well.

similarly all angle equal triangle is isosceles as well as equilateral trangle.
_________________

Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html

GT

Director
Joined: 27 May 2008
Posts: 549
Followers: 8

Kudos [?]: 312 [0], given: 0

### Show Tags

30 Jul 2008, 21:37
interesting ....

http://en.wiktionary.org/wiki/isosceles_triangle

i fail to understand the logic of these old guys .... is there a specific property of isosceles traingle, which is not applied to equilateral triangle..... i mean even 300 years ago, these guys were very intelligent and if they have defined is this way there has to be a logic ... right ?
Director
Joined: 20 Sep 2006
Posts: 658
Followers: 2

Kudos [?]: 111 [0], given: 7

### Show Tags

30 Jul 2008, 21:48
AGREE .... All I can say is that ...this is GMAT ... so lets say that OG is GOD and whatwever OG says is true.

"the Official Guide defines an isosceles triangle as one with 'at least two equal sides', so equilateral triangles are officially isosceles on the GMAT"
Re: geometery confusion   [#permalink] 30 Jul 2008, 21:48
Display posts from previous: Sort by