gmatusa2010 wrote:If <(ABC)= 90 degrees, does this mean that angle B is 90 degree?

In General, Yes. But depends on the diagram. If you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: I've actually seen two different problems 1) Angle B is definitely 90 degree

If you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: 2) You can't assume that. You just know that triangle made by the points A,B, and C make a 90 degree angle somewhere.

Yes, you cannot assume that because there might be another traingle inside ABC. See the image below DBC is another triangle residing inside ABC. If you say angle B it can either mean angle ABC which is 90, or mean angle DBC which is less than 90. Thus, if you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: Is there an official standard for GMAC?

No, I dont think this kind of ambiguity will arise in GMAT.

shovan85 wrote:

gmatusa2010 wrote:If <(ABC)= 90 degrees, does this mean that angle B is 90 degree?

In General, Yes. But depends on the diagram. If you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: I've actually seen two different problems 1) Angle B is definitely 90 degree

If you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: 2) You can't assume that. You just know that triangle made by the points A,B, and C make a 90 degree angle somewhere.

Yes, you cannot assume that because there might be another traingle inside ABC. See the image below DBC is another triangle residing inside ABC. If you say angle B it can either mean angle ABC which is 90, or mean angle DBC which is less than 90. Thus, if you were said in triangle ABC, angle ABC is 90 that means angle B of the triangle ABC is 90.

gmatusa2010 wrote: Is there an official standard for GMAC?

No, I dont think this kind of ambiguity will arise in GMAT.

I guess GMAT will explicitly mention which <B they are mentioning.

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