# Using both subscripted and non-subscripted variables in an equation

I'm getting started with Mathematica, as I have been using Maple in the past. Is it possible to define two variables $$\alpha_1, \alpha_2$$ and then still use $$\alpha$$ as a parameter of a function and, for example, plot it.

$$\alpha_1:=5$$ $$\alpha_2:=10$$

$$a:=\sum_{i=1}^{2}\alpha_i \cdot \alpha$$

Plot[a,{α,0,10}]


I have found that I have to use a different variable, such as $$\tilde{\alpha}$$ for that to work. Any way around that?

On a side note, is it possible to have Mathematica treat an expression such as $$a_b$$ as one variable, but still understand subscripts on other defined variables such as $$a_1, a_2, …$$? I understand that the Symbolize package is used for that, but did not quite get how to symbolize only specific expressions.

I apologize for my lack of deeper understanding in Mathematica, but that's what you get when you use something as soothing to the eye as Maple ;)

As you say, it is best not to use the same variable inside and outside of Subscript. However, nothing is stopping you from using a string inside of Subscript:

Subscript["α", 1] = 5;
Subscript["α", 2] = 10;

a := Sum[Subscript["α", i] α, {i, 2}]

Plot[a, {α, 0, 10}]


Can you explain why you need to treat $$a_b$$ as one variable?

• It is a mostly readability - "ab" would of course work as a variable, but ultimately I want to print my worksheets and then have them look nice. I've been using the Palettes (Basic Math Assistant) for graphical fractions etc. for that very purpose. Am I confusing Mathematica too much with LaTeX? Sep 24 '18 at 14:59
• @Wasserwaage In what context does Subscript[a, b] (or Subscript["a", "b"]) not work as a variable? Sep 24 '18 at 15:01
• It works, I am just trying to keep the potential for errors in my worksheet to a minimum - and defining Subscript[a,b] would have seemed like a sensible way to do that. Thanks! Sep 24 '18 at 15:20