Really hard SAT math question...

Test Preparation SAT Preparation
1

<p>This one from a while ago, but I've been trying to crack it and cant:</p>

<ul>
<li>Show that in triangle ABC, if angle C is acute, then c < the square root of a^2 + b^2, and if angle C is obtuse, c > the square root of a^2 + b^2.</li>
</ul>

2

<p>This can’t be such a “really hard” question. Check this out: [Law</a> of cosines - Wikipedia, the free encyclopedia](<a href=“http://en.wikipedia.org/wiki/Law_of_cosines]Law”>Law of cosines - Wikipedia).</p>

3

<p>Law of Cosines:
c^2 = a^2 + b^2 - 2ab cos C
=>
c = sqrt(a^2 + b^2 - 2ab cos C)</p>

<p>If C > 90 (obtuse), cos C is negative,
=>
c = sqrt(a^2 + b^2 + some positive value)
=>
c > sqrt(a^2 + b^2)</p>

4

<p>This is not a SAT math question. More importantly, I’m pretty sure no problem tests knowledge of the law of cosines.</p>

5

<p>This is SAT II question (even lvl 2 one)</p>

6

<p>SAT math is multiple choice, not proof based. therefore, this is actually a poorly disguised homework help thread.</p>