Why its showing this error?

for 1st you I equations I gave coding it accepted

and when I code the third one

it told me this Error using symfun/assume (line 12)

Assumptions on symbolic functions not supported. Make assumptions on symbolic variables and expressions instead

can anyone help me to figure this out why

[Stephan]

Please provide the whole code and the complete error message you get.

Answer 1

[Walter Roberson]

It is not permitted to use

syms S_1(x) positive    %or negative or real or any other flag
assume(S_1, 'positive') %or any other flag
assume(S_1 > 0)         %or any other condition

Note that if you used

assume(S_1(x), 'positive') %or any other flag
assume(S_1(x) > 0)         %or any other condition

then those would be permitted. S_1 in this context is a symfun, but S_1(x) is the result of invoking S_1 upon x, and so is a symbolic expression rather than a symfun.

[Avinash T]

Bro why we are using those those % comments is those comments play a maojr role.

[Walter Roberson]

The % comments play the major roll of documenting that the issue is not the flag positive alone, and that the same problem occurs for each of the documented symbolic flags.

[Walter Roberson]

https://www.mathworks.com/help/symbolic/syms.html#buod73_-set

The known flags are

• real
• positive
• integer
• rational

You cannot use any of those in connection with declaring a function with syms

All of the following are wrong

• syms f(x) real
• syms f(x) positive
• syms f(x) integer
• syms f(x) rational

[Avinash T]

Thanks bro I learned this from you.