Solving Homework Questions: Modulus, Arg, Roots

In summary, Vela suggests that students and helpers should avoid posting images only and type out the problem if it is not long and/or complicated.
  • #1
King_Silver
83
6

Homework Statement


First question = attached below
Second Question = attached below

Homework Equations


modulus, argument, roots.

The Attempt at a Solution


For the 1st question I've gotten the modulus, the principal argument and the abs. of z^1/4 which was something like 1.5335 I believe. The only thing I am not understanding with regards to this question is the final part, where it is asking for the smallest argument, 2nd smallest, 2nd largest and largest in that ascending order.
I've tried several things but none of them have worked to give me a proper answer. I'm probably missing something really stupid like "Just divide it by x to find smallest, add x to find largest, take away x to find second smallest" or some standard format like that.

2nd question I got these as my answers
1: e^(3x)
2: -3y

3: -(i*arg(-2+4i))/3 + ln(abs(-2+4i))/3

yet they don't seem to be the correct answers, I think I must be leaving out a step in the 2nd one.
 

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  • #2
King_Silver said:

Homework Statement


First question = attached below
Second Question = attached below

Homework Equations


modulus, argument, roots.

The Attempt at a Solution


For the 1st question I've gotten the modulus, the principal argument and the abs. of z^1/4 which was something like 1.5335 I believe. The only thing I am not understanding with regards to this question is the final part, where it is asking for the smallest argument, 2nd smallest, 2nd largest and largest in that ascending order.
I've tried several things but none of them have worked to give me a proper answer. I'm probably missing something really stupid like "Just divide it by x to find smallest, add x to find largest, take away x to find second smallest" or some standard format like that.

2nd question I got these as my answers
1: e^(3x)
2: -3y

3: -(i*arg(-2+4i))/3 + ln(abs(-2+4i))/3

yet they don't seem to be the correct answers, I think I must be leaving out a step in the 2nd one.
I suggest that these should be posted two threads, one thread for each problem. They are not all that similar, and each is multi-part.

It would be helpful to post the images as full-size like this:

math-2-png.95272.png
 
  • #3
King_Silver said:

Homework Statement


First question = attached below
Second Question = attached below

Homework Equations


modulus, argument, roots.

The Attempt at a Solution


For the 1st question I've gotten the modulus, the principal argument and the abs. of z^1/4 which was something like 1.5335 I believe. The only thing I am not understanding with regards to this question is the final part, where it is asking for the smallest argument, 2nd smallest, 2nd largest and largest in that ascending order.
I've tried several things but none of them have worked to give me a proper answer. I'm probably missing something really stupid like "Just divide it by x to find smallest, add x to find largest, take away x to find second smallest" or some standard format like that.
When you are asked to calculate something like z1/n, you should be aware that there are n separate and distinct complex numbers, call them w1, w2, w3, ..., wn, which result. These complex numbers are related to what are known as the roots of unity, which is described here:

https://en.wikipedia.org/wiki/Root_of_unity

If you express the original complex number z in its polar form, such that z = r e i θ, then the various values of z1/n can be easily computed.
 
  • #4
King_Silver said:

Homework Statement


First question = attached below
Second Question = attached below

Homework Equations


modulus, argument, roots.

The Attempt at a Solution


For the 1st question I've gotten the modulus, the principal argument and the abs. of z^1/4 which was something like 1.5335 I believe. The only thing I am not understanding with regards to this question is the final part, where it is asking for the smallest argument, 2nd smallest, 2nd largest and largest in that ascending order.
I've tried several things but none of them have worked to give me a proper answer. I'm probably missing something really stupid like "Just divide it by x to find smallest, add x to find largest, take away x to find second smallest" or some standard format like that.

2nd question I got these as my answers
1: e^(3x)
2: -3y

3: -(i*arg(-2+4i))/3 + ln(abs(-2+4i))/3

yet they don't seem to be the correct answers, I think I must be leaving out a step in the 2nd one.

You should avoid posting images only. Type out the problem if it is not long and/or complicated. Type out you solution also, to the extent possible. As Vela states in his post "Guidelines for students and helpers": "Ask yourself "If I can't be bothered to spend my time typing it, why should they be bothered to spend their time reading it, much less responding to it?" Use images for supporting figures."
 

Related to Solving Homework Questions: Modulus, Arg, Roots

1. How do I solve a homework question involving modulus?

In order to solve a homework question involving modulus, you must first understand what modulus is. Modulus, denoted by the symbol "|" (vertical bars), is used to find the remainder when dividing two numbers. To solve a modulus question, you can use the formula a mod b = r, where a is the dividend, b is the divisor, and r is the remainder. Simply plug in the given values and solve for r.

2. What is the Arg function and how is it used?

The Arg function, short for argument, is used to find the angle or phase of a complex number in polar form. It is denoted by Arg(z) or arg(z), where z is a complex number. To find the Arg of a complex number, you can use the formula Arg(z) = tan-1 (Im(z)/Re(z)), where Im(z) is the imaginary part of the complex number and Re(z) is the real part.

3. How do I find the roots of a polynomial equation?

To find the roots of a polynomial equation, you can use the quadratic formula or synthetic division. The quadratic formula is used for equations in the form ax2 + bx + c = 0, where a, b, and c are constants. Synthetic division is used for equations in the form x = a, where a is a constant. Both methods involve plugging in the given values and solving for the roots.

4. Can I use the quadratic formula to solve equations with complex roots?

Yes, you can use the quadratic formula to solve equations with complex roots. Complex roots come in the form of a+bi, where a and b are real numbers and i is the imaginary unit. When using the quadratic formula, the discriminant (b2 - 4ac) will be negative, indicating that the roots are complex. You can then use the formula x = (-b ± √(b2 - 4ac))/2a to solve for the complex roots.

5. What is the difference between real and complex roots?

Real roots are solutions to an equation that are real numbers. They can be found using methods such as the quadratic formula or synthetic division. Complex roots, on the other hand, are solutions that involve the imaginary unit i. They are often found in equations with non-real coefficients and can be determined using the quadratic formula as well. Real roots lie on the real number line, while complex roots lie on the imaginary number line.

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