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QUESTION: Dear Dr. Patton, I'm a bit stuck with complex numbers. In this exercise (see attachment) I am asked to simplify each of the following expressions to either the standard or exponential form.

I'm a bit confused and I don't know where I should start from.

I look forward to hearing from you.

Thanks in advance

Best regards

ANSWER: Expressions with complex numbers look, well, complicated, but they are easy to manipulate. For your problem you need to use just a few straightforward definitions, including:

Combining exponents:

(x^n)(x^m) = x^(n+m)

(x^n)^m = x^(nm)

(x^n)/(x^m) = (x^n)(x^(-m)) = x^(n-m).

Complex number relations (where j = sqrt(-1)):

for z = x + iy = complex number we have Re(z) = x and Im(z) = y

e^(jx) = cosx + isinx

(e^jx)^n = e^(jxn) so that (cosx + isinx)^n = cos(xn) + isin(xn) <-- this is a biggy (de Moivre's thm).

Using these relations, you can simplify the expressions as in the attached image.

BTW, here are 2 other relations you should keep in your quiver:

cosx = (e^jx + e^-jx)/2 & sinx = (e^jx - e^-jx)/2i.

Randy

---------- FOLLOW-UP ----------

QUESTION: Dear Dr. Patton, first of all thanks for your extremely quick reply. Just another question, when you say "you can simplify the expressions as in the attached image", is there supposed to be any image attachment? I couldn't find nothing.

Sorry for this silly question.

Best regards

Stefano

Not a silly question. I did attach an image with the "solutions" in my previous answer so I am wondering what happened to it. I checked the "Answered Questions" selection and it was there, along with your original image.

Whatever, I'll attach the image again with the website SW. Let me know if you don't receive it.

Randy

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