Alan G. answered 07/01/16
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Mustafa,
Basically what you need here are the four 4th roots of the complex number −7 − 12i.
The steps to do this are as follows:
1) Write the number in trigonometric form: −7 − 12i = √193 cis 192.18°.
2) Use the nth Root Theorem to find all four roots:
wk = (√193)1/4 cis (192.18°/4 + 360°k/4) for k = 0, 1, 2, 3
After plugging in and simplifying you will get
w0 = 8√193 cis 48.04°
w1 = 8√193 cis 138.04°
w2 = 8√193 cis 228.04°
w3 = 8√193 cis 318.04°
You can then use the definition of cis θ = cos θ + i sin θ to write these four complex numbers in standard form x + yi. You will need to do this using your own calculator. As you did not specify how the answers were to be given, I cannot finish the problem for you. The x and y values of the answers will probably all involve decimals. You must round them as requested in the original problem.