Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 8 - Section 8.4 - Roots of a Complex Number - 8.4 Problem Set - Page 447: 34

Answer

The five fifth roots are: $96.59+25.88 i, \quad 5.23+99.86 i, \quad-93.36+35.84 i, \quad-62.93-77.71 i, \quad 54.46-83.87 i$

Work Step by Step

\[ =10^{10}\left[\cos 75^{\circ}+i \sin 75^{\circ}\right]=10^{10} \text { cis } 75^{\circ} \] Using the roots theorem: \[ \left[\cos \left(\frac{\theta}{n}+\frac{360^{\circ}}{n} k\right)+i \sin \left(\frac{\theta}{n}+\frac{360^{\circ}}{n} k\right)\right]r^{\frac{1}{n}}=w_{k} \] When $0=k$ : \[ \left(10^{10}\right)^{\frac{1}{3}}\left[\cos \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(0)\right)+i \sin \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(0)\right)\right]=w_{0} \] Simplify: \[ =10^{2}\left[\cos 15^{\circ}+i \sin 15^{\circ}\right] \] Using a calculator: \[ =[0.9659+0.2588 i]100 \] Multiply: \[ =96.59+25.88 i \] When $1=k$ : \[ \left(10^{10}\right)^{\frac{1}{5}}\left[\cos \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(1)\right)+i \sin \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(1)\right)\right]=w_{1} \] Simplify: \[ \begin{array}{c} =10^{2}\left[\cos \left(15^{\circ}+72^{\circ}\right)+i \sin \left(15^{\circ}+72^{\circ}\right)\right] \\ =100\left[\cos 87^{\circ}+i \sin 87^{\circ}\right] \end{array} \] Using a calculator: \[ =1[0.0523+0.9986 i]100 \] Multiply: \[ = \] When $2=k$ : \[ \left[\cos \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(2)\right)+i \sin \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(2)\right)\right]\left(10^{10}\right)^{t}=w_{2} \] Simplify: \[ \begin{array}{c} =10^{2}\left[\cos \left(15^{\circ}+144^{\circ}\right)+i \sin \left(15^{\circ}+144^{\circ}\right)\right] \\ =100\left[\cos 159^{\circ}+i \sin 159^{\circ}\right] \end{array} \] Using a calculator: \[ =1[-0.9336+0.3584 i]100 \] Multiply: When $3=k$ : \[ \left(10^{10}\right)^{\frac{1}{5}}\left[\cos \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(3)\right)+i \sin \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(3)\right)\right]=w_{3} \] Simplify: \[ \begin{array}{c} =10^{2}\left[\cos \left(15^{\circ}+216^{\circ}\right)+i \sin \left(15^{\circ}+216^{\circ}\right)\right] \\ =100\left[\cos 231^{\circ}+i \sin 231^{\circ}\right] \end{array} \] Using a calculator: \[ =[-0.6293-0.7771 i]100 \] Multiply: When $4=k$ : \[ \left(10^{10}\right)^{\frac{1}{5}}\left[\cos \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(4)\right)+i \sin \left(\frac{75^{\circ}}{5}+\frac{360^{\circ}}{5}(4)\right)\right]=w_{4} \] Simplify: \[ \begin{array}{c} =10^{2}\left[\cos \left(15^{\circ}+288^{\circ}\right)+i \sin \left(15^{\circ}+288^{\circ}\right)\right] \\ =10^{2}\left[\cos 303^{\circ}+i \sin 303^{\circ}\right] \end{array} \] Using a calculator: \[ =[0.5446-0.8387 i]100 \] Multiply: \[ =54.46-83.87 i \]
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.