How to properly use Symbolic Toolbox to implement superscripts and subscripts on imaginary numbers and theta

Greetings community,

I'll begin by saying that I am not an engineer or math expert. This question arose during my independent research to understand kinematics, more specifically complex number addition and vector loops.

Part of this expirement is that I want to learn more about properly using the Symbolic Toolbox to be able to write expressions as seen in this image snippet. However, I am failing to use the superscripts and subscripts properly. Consider the following code snippet:

syms V1 theta_1 i

V1_expr = V1 * exp(theta_1 * 1i)

As the more educated person can see, it will not produce the desired outcome as shown in the image above. It will subscript theta with 1. Instead I have tried to subscript the imaginary number but MatLab gets upset when I do that. What I get as a result that works right now is:

Would anyone be willing to assist me?

Cheers,

[Walter Roberson]

Be careful. If you use

syms V1 theta_1 i
V1_expr = V1 * exp(theta_1 * i)

then i is treated as just another symbol, instead of as the special constant sqrt(-1)

Answer 1

[Aneela]

Hi @Clayton Allen

The "syms" function in MATLAB's Symbolic Toolbox allows you to create symbolic scalar variables and functions, and matrix variables and functions.

The code below generates desired expression:

syms V1 theta1 i
V1_expr = V1 * exp(i * theta1);
disp(V1_expr);

Please refer to the following MathWorks documentation for more information on "syms": https://www.mathworks.com/help/symbolic/syms.html

[Walter Roberson]

This is the same code that @Clayton Allen already posted, but Clayton got a different result.

Probably Clayton is using regular .m files. Fancy formatting is not available for regular .m files.

Fancy formatting is available for LiveScript (and MATLAB Online, and MATLAB Answers)

[Clayton Allen]

I can confirm @Walter Roberson this was created using an MLX file type. That's how I was able to grab the screen snip of the output posted above.

Cheers,

[Clayton Allen]

@Aneela,

The error in my script as you pointed out was using:

V1_expr = V1 * exp(1i * theta_1)

Instead of:

V1_expr = V1 * exp(i * theta_1)

Thanks for your assistance.

Cheers,

[Walter Roberson]

In LiveScript, both expressions are the same.

Unfortunately due to a bug in MATLAB Answers, I cannot show you the outputs. (They are there... just not showing up.)

clear i               %MATLAB Answers glitch, i initialized as [] sometimes
syms V1 theta_1
V1_expr = V1 * exp(theta_1 * 1i);
disp(V1_expr)
V2_expr = V1 * exp(theta_1 * i);
disp(V2_expr)

[Clayton Allen]

Oh... That is a good catch! I went in and tested the values out and found what you pointed out.