Math 2 Question (Barron's)

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1

<p>I just did the Barron's Diagnostic Test today, and there's one question I don't understand.</p>

<ol>
<li>If A=arctan(-3/4) and A+B=315, then B=...
A. 278.13
B. 351.87
C. -8.13
D. 171.87
E. 233.13</li>
</ol>

<p>The answer, according to the book, is B. But why can't it also be D? The calculator value of the arctan is -36.87, which explains B, but A = -36.87 + 180 also satisfies the arctan, which would explain D. How do I know which is the correct value?</p>

2

<p>The range of tan^(-1) is (-90°, 90°). So arctan(-3/4) = -36.87°.</p>

3

<p>^ Is that the rule? When the range is not stated, then you assume that’s the standard range? I mean, why can’t the range of arctan be (90, 270?)</p>

4

<p>I’m pretty sure it’s defined to be (-90, 90), so that arctan is a function.</p>

5

<p>I see. Thanks, MIT guy.</p>