grab one side of an equation

Question

Is there a simple way to grab or reference one side of an equation?

Minimal example of what I mean:

    eq = x^2==3x
    (*Pseudo Code*)
    in: Grab_lefthandside(eq)
    out: x^2

@AskingQuestions. Everything (basically) in Mathematica is an expression of which you can take Parts. Sin[x][[1]] gives x, for instance. Even Graphics` objects: look at FullForm[Plot[x, {x, 0, 1}]]. — march, Aug 30, 2016 at 16:43

Vahagn Tumanyan · Accepted Answer · 2016-08-30 14:10:24Z

3

You can change Equal to List and you will have the list of left and right hand sides of the equation.

First[List @@ (x^2 == 3 x)]

answered Aug 30, 2016 at 14:10

Vahagn Tumanyan

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3

$\begingroup$ Part, First, Last, etc. operate on expressions not just a List. There is no need to convert to a List to use them. Try f[a, b, c] // First $\endgroup$
– Bob Hanlon
Aug 30, 2016 at 15:27
$\begingroup$ That is true. However, I wanted to show how one can extract and manipulate all the objects in an expression. $\endgroup$
– Vahagn Tumanyan
Aug 31, 2016 at 5:56

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