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Limit[expr,x->Subscript[x, 0],Direction->1] computes the limit as x approaches Subscript[x, 0] from smaller values. Limit[expr,x->Subscript[x, 0],Direction->-1] computes the limit as x approaches Subscript[x, 0] from larger values.

This to me is confusing, I though x->4- that x are approaching xo from smaller values, in other words from the left hand side. Why would one therefore use 1 for left hand side and -1 for right hand side. Do not see the logic

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  • $\begingroup$ Approaching direction corresponds to the direction of axis for example. $\endgroup$ – Kuba Jul 9 '14 at 8:02
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    $\begingroup$ Think of it as the direction you're going, not the direction you're coming from. (Although I do agree with you that it is a little inconsistent with the traditional mathematical notation. Perhaps they should have just used Above and Below for no chance of confusion.) $\endgroup$ – Rahul Jul 9 '14 at 9:19
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Think of it as the direction you're going, not the direction you're coming from. (Although I do agree with you that it is a little inconsistent with the traditional mathematical notation. Perhaps they should have just used Above and Below for no chance of confusion.)

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    $\begingroup$ "Above" and "Below" would be problematic when discussing unreal (surreal?) approaches in the complex plane. $\endgroup$ – Daniel Lichtblau Dec 17 '15 at 22:11

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