Find the modulus of the complex number $5 - 12i$.
A$13$CORRECT
B$\sqrt{119}$
C$7$
D$17$
JUPEBMathematicsComplex Numbers
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Why the answer is A, and why the others tempt you.
$|5 - 12i| = \sqrt{5^2 + (-12)^2} = \sqrt{25 + 144} = \sqrt{169} = 13$. Subtracting the squares gives $\sqrt{119}$, and adding or subtracting the coefficients directly gives 17 or 7.
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