# keep from evaluating a symbolic expression

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Answered: Walter Roberson on 5 Jul 2022
Utter noob question but Im trying to build up a function and see it in with nice formatting in live script how do I keep it from evaluating?
Say below I want to make sure that I have typed it in correctly not auto evaluate it . Also is there anyway to use e as asymbol and not have it automatically evaluate it into its fractional form? Sorry for how basic this is Im sadly only on hour number 3 of this langauge .
4*pi^2 * (2*pi*100)^2 *1/5
Abhijeet on 4 Jul 2022
In the sentence "Also is there anyway to use e as asymbol", here 'e' is an exponential constant?
Walter Roberson on 4 Jul 2022
Pi = sym(pi);
E = exp(sym(1));
4*Pi^2 * (2*E*100)^2 * 1/5
ans =

Abhijeet on 4 Jul 2022
I understand you want to visualize the expression without it getting evaluated.
This can be achieved using symbolic variables, but still, constants will be evaluated to a simplified expression.
Create ‘pi’ as a symbolic variable as demonstrated below:
Use 'e' as a symbolic variable to represent ‘e’ as an exponent constant without it getting evaluated.
Here is a demonstration to create symbolic variables:
For more insights on symbolic variables, kindly visit the below mentioned hyperlinks:
Walter Roberson on 5 Jul 2022
There was a long period during which
syms pi
would make pi into a symbolic variable that referred to the transcendental constant π. However, that is no longer the case; now syms pi makes pi into an ordinary variable that does not refer to the constant (the situation is a little stranger than that internally.)
These days, to get LiveScript to display π for values that refer to the transcendental constant, use
pi = sym(pi);
or do like I did, of using Pi for that purpose instead, so that the numeric pi remains accessible.
See the difference:
syms pi
vpa(pi)
ans =
π
clear pi
pi = sym(pi)
pi =
π
vpa(pi)
ans =
3.1415926535897932384626433832795
Awesome , thanks for yalls help

Walter Roberson on 5 Jul 2022
You can use displayFormula on the character (or string()) version of the formula, and later convert that to symbolic
as_char = '4*pi^2 * (2*pi*100)^2 *1/5'
as_char = '4*pi^2 * (2*pi*100)^2 *1/5'
displayFormula(as_char)
as_sym = str2sym(as_char)
as_sym =

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