SOLUTION: 1. Find the modulus and argument of the following complex numbers, and write them in trigonometric form: a. 5 – 8i b. –1 – i c. –5 + 12i d. 1 + √3i 2. Express each of

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: 1. Find the modulus and argument of the following complex numbers, and write them in trigonometric form: a. 5 – 8i b. –1 – i c. –5 + 12i d. 1 + √3i 2. Express each of      Log On

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Question 1117670: 1. Find the modulus and argument of the following complex numbers, and write them in trigonometric form:
a. 5 – 8i
b. –1 – i
c. –5 + 12i
d. 1 + √3i
2. Express each of the following complex numbers in the rectangular form: a + bi.
a. 2 (cos30° + i sin 30°)
b. √2 (cos135° + i sin 135°)
c. 5 cis(255°)
d. √3 cis (11π/6)

Answer by ikleyn(52781) About Me  (Show Source):
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1. Find the modulus and argument of the following complex numbers, and write them in trigonometric form:


            HINT.   For complex number  z = a + bi  the modulus   |z| = r = sqrt%28a%5E2+%2B+b%5E2%29;   argument t = arctan%28b%2Fa%29  with correction for a quadrant;
                          Trigonometric form is   z = r*(cos(t) + i*sin(t)).


a.	5 – 8i       Modulus  sqrt%285%5E2%2B%28-8%29%5E2%29 = sqrt%2889%29.   

                     Argument  t = arctan%28-8%2F5%29.

                     Trigonometric form  5 - 8i = sqrt%2889%29%2A%28cos%28t%29+%2B+i%2Asin%28t%29%29.



b.	–1 – i       Modulus   sqrt%28%28-1%29%5E2%2B%28-1%29%5E2%29 = sqrt%282%29.

                     Argument  t = arctan%28%28-1%29%2F%28-1%29%29+%2B+pi = pi%2F4+%2B+pi = 5pi%2F4   (in QIII)

                     Trigonometric form  -1-i = sqrt%282%29%2A%28cos%285pi%2F4%29+%2B+i%2Asin%285pi%2F4%29%29.



c.	–5 + 12i      Modulus   sqrt%28%28-5%29%5E2%2B12%5E2%29 = sqrt%2825%2B144%29 = sqrt%28169%29 = 13.

                      Argument  t = arctan%28-12%2F5%29%2Bpi = -arctan%2812%2F5%29%2Bpi  in QII.

                      Trigonometric form  -5 + 12i = 13*(cost)+i*sin(t)).



d.	1 + sqrt%283%29i      Modulus  sqrt%281%5E2%2B%28sqrt%283%29%29%5E2%29 = sqrt%281%2B3%29 = 2.

                      Argument  t = arctan%28sqrt%283%29%29 = pi%2F3.

                      Trigonometric form   1 + sqrt%283%29%2Ai = %28cos%28pi%2F3%29+%2B+i%2Asin%28pi%2F3%29%29.




2.	Express each of the following complex numbers in the rectangular form: a + bi.

a.	2 (cos30° + i sin 30°)          = 2%2A%28sqrt%283%29%2F2+%2B+i%2A%281%2F2%29%29 = sqrt%283%29+%2B+i.


b.      √2  (cos135° + i sin 135°)      = sqrt%282%29%2A%28-sqrt%282%29%2F2+%2B+i%2A%28sqrt%282%29%2F2%29%29 = -1 + i.


c.	5 cis(255°)                     = 5%2A%28cos%28255%5Eo%29+%2B+i%2Asin%28255%5Eo%29%29 = 5%2Acos%28255%5Eo%29+%2B+5%2Asin%28255%5Eo%29%2Ai.


d.	 √3 cis (11π/6)      = sqrt%283%29%2A%28cos%2811pi%2F6%29+%2B+i%2Asin%2811pi%2F6%29%29 = sqrt%283%29%2A%28sqrt%283%29%2F2+%2B+i%2A%28-1%2F2%29%29 = 3%2F2+-+i%2A%281%2F2%29 = 1.5 - 0.5*i.

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             * * * Completed and solved. * * *
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On complex numbers, see introductory lessons
    - Complex numbers and arithmetical operations on them
    - Complex plane
    - Addition and subtraction of complex numbers in complex plane

    - Solved problems on taking roots of complex numbers
    - Solved problems on arithmetic operations on complex numbers
    - Solved problem on taking square root of complex number
in this site.

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Complex numbers".


Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.