General triangle rule (30:60:90)

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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General triangle rule (30:60:90)

by tgf » Sun Nov 29, 2009 2:51 am
Hi, if a right triangle has one angle equal to 30 (or 60) you KNOW the other angle has to be 60 (or 30) and thus the longest side is 2 times the shortest side.

Does this equivalency work both ways? (I can't get a clear sense of it from various answer guides and just want to make sure)

If you know a right triangle has the longest side equal to two times the shortest side, do you then KNOW it HAS to be a 30:60:90 triangle?

Thanks
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by DanaJ » Sun Nov 29, 2009 3:28 am
The answer is yes, you know it's a 30-60-90. However, I don't really feel that good about using "longest" and "shortest" to describe sides. The longest side of a triangle will always be the hypotenuse and I prefer this terminology :)

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by tgf » Sun Nov 29, 2009 3:49 am
Okay, thanks, that was good to know.