Find the trigonometric form of the complex number shown below.
-7 - i
A) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 2 } { 21 } \right) \right) + i \sin \left( \arctan \left( \frac { 2 } { 21 } \right) \right) \right)$
B) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( - \frac { 3 } { 7 } \right) \right) + i \sin \left( \arctan \left( - \frac { 3 } { 7 } \right) \right) \right)$
C) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( - \frac { 3 } { 35 } \right) \right) + i \sin \left( \arctan \left( - \frac { 3 } { 35 } \right) \right) \right)$
D) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 1 } { 7 } \right) \right) + i \sin \left( \arctan \left( \frac { 1 } { 7 } \right) \right) \right)$
E) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 1 } { 14 } \right) \right) + i \sin \left( \arctan \left( \frac { 1 } { 14 } \right) \right) \right)$

Question

Find the trigonometric form of the complex number shown below.  
-7 - i
A)  $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 2 } { 21 } \right) \right) + i \sin \left( \arctan \left( \frac { 2 } { 21 } \right) \right) \right)$
B)  $5 \sqrt { 2 } \left( \cos \left( \arctan \left( - \frac { 3 } { 7 } \right) \right) + i \sin \left( \arctan \left( - \frac { 3 } { 7 } \right) \right) \right)$
C)  $5 \sqrt { 2 } \left( \cos \left( \arctan \left( - \frac { 3 } { 35 } \right) \right) + i \sin \left( \arctan \left( - \frac { 3 } { 35 } \right) \right) \right)$
D)  $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 1 } { 7 } \right) \right) + i \sin \left( \arctan \left( \frac { 1 } { 7 } \right) \right) \right)$
E) $5 \sqrt { 2 } \left( \cos \left( \arctan \left( \frac { 1 } { 14 } \right) \right) + i \sin \left( \arctan \left( \frac { 1 } { 14 } \right) \right) \right)$

Quizplus · Accepted Answer

The modulus of the complex number -7 - i is $\sqrt{(-7)^2 + (-1)^2} = \sqrt{49 + 1} = \sqrt{50} = 5\sqrt{2}$. The argument is $\arctan\left(\frac{-1}{-7}\right) = \arctan\left(\frac{1}{7}\right)$. Thus, the trigonometric form is $5\sqrt{2}(\cos(\arctan(\frac{1}{7})) + i\sin(\arctan(\frac{1}{7})))$.

Find the Trigonometric Form of the Complex Number Shown Below