DS----Is a^2 + b^2<15?

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nitya34: Master | Next Rank: 500 Posts; Posts: 179; Joined: Tue Jan 08, 2008 7:23 pm; Thanked: 11 times; GMAT Score:590

by nitya34 » Mon Jul 20, 2009 3:12 am

Is the degree measure of one of the interior angles of triangle ABC greater than 90? [a, b, and c are sides of the triangle.]
(1) a^2+b^2<15[edited]
(2) c >4

OA says .....[spoiler]...C.......Together, a^2+b^2<c^2. SUFF..........is it E.[/spoiler]...........?

Last edited by nitya34 on Tue Jul 21, 2009 2:43 am, edited 2 times in total.

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Source: Beat The GMAT — Data Sufficiency | Mon Jul 20, 2009 3:12 am

axat: Senior | Next Rank: 100 Posts; Posts: 70; Joined: Wed Jun 25, 2008 8:33 pm; Thanked: 3 times

by axat » Mon Jul 20, 2009 4:01 am

You are posting some excellent questions Nitya34.

You missed raising A to the power of 2.

it is C. There are these 3 properties that explain whether a triabgle is acute, obtuse or right angle.

if a^2 + b^2 = c^2, then it's a right angle triangle.
if a^2 + b^2 < c^2, then it's an obtuse angled triangle
if a^2 + b^2 > c^2, then it's an acute angled triangle.

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raghavsarathy: Master | Next Rank: 500 Posts; Posts: 166; Joined: Sat Apr 18, 2009 10:41 pm; Thanked: 9 times; GMAT Score:770

by raghavsarathy » Mon Jul 20, 2009 9:54 am

Hey Nitya34

What is the source of this question.. I am posting it here itself instead of a PM because others would also surely be interested to refer that source !

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axat: Senior | Next Rank: 100 Posts; Posts: 70; Joined: Wed Jun 25, 2008 8:33 pm; Thanked: 3 times

by axat » Mon Jul 20, 2009 11:14 am

Yes, Nitya34, I want to know the source too.

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Domnu: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun May 24, 2009 3:55 pm; Thanked: 11 times; GMAT Score:740

by Domnu » Mon Jul 20, 2009 12:26 pm

Generally, for a triangle, we have that

A^2 + B^2 = C^2 for a right triangle
A^2 + B^2 < C^2 for an obtuse triangle
A^2 + B^2 > C^2 for an acute triangle (for all ways)

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nitya34: Master | Next Rank: 500 Posts; Posts: 179; Joined: Tue Jan 08, 2008 7:23 pm; Thanked: 11 times; GMAT Score:590

by nitya34 » Tue Jul 21, 2009 2:39 am

thanks axat
source-googling......

axat wrote:There are these 3 properties that explain whether a triabgle is acute, obtuse or right angle.

if a^2 + b^2 = c^2, then it's a right angle triangle.
if a^2 + b^2 < c^2, then it's an obtuse angled triangle
if a^2 + b^2 > c^2, then it's an acute angled triangle.

Many of the great achievements of the world were accomplished by tired and discouraged men who kept on working.

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