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Special Triangles Question

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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by giatch » Mon Dec 29, 2008 12:58 pm
Could someone please clear up something for me..

For the special triangles, i.e.

1) 3:4:5 with side 5 opposite the right angle
2)12:5:3 with 13 opposite the right angle

What are the measure of the other two angles for these two respective triangles?

Does it matter? Will it be the 30:60:90 triangle or something else?
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by Ian Stewart » Mon Dec 29, 2008 1:17 pm
To work out the angles in a 3-4-5 or 5-12-13 triangle, you'd need to use trigonometry (sine, cosine, etc) - in other words, not something you'd ever need for the GMAT. If I remember right, the 3-4-5 has angles something like 38-52-90, rounded to the nearest integer, but you certainly don't need to know that for the test. They are certainly not 30-60-90 triangles, since every 30-60-90 triangle has sides which are in a 1-root(3)-2 ratio.
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by rajataga » Sun Jan 04, 2009 8:14 pm
The only thing that you might need to keep in mind is that both the groups that you have given are 'pythagorean triplets'. Meaning they are the sides of a triangle forming a right angled triangle.

I've seen in some sums it is helpful to keep in mind the basic pythagorean triplets

THe angle opposite the largest side will always be the right angle.

So, if you see these sides for a triangle, you know that it is a right angled triangle, and also the right angle.
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