So I apologize if this question seems a bit nit-picky, but it has bothered me for a while. Usually when a coordinate system is represented in two-dimensions, the x-axis is pointing towards what might be considered "3 o' clock", while the y-axis is at midnight.

two dimensional coordinate system

However, most representations of 3-dimensional space place the x-axis in the "6 o' clock" direction, and the Y axis in the "3 o'clock" direction.(if you were to lay the clock on the x-y plane).three dimensional coordinate system

It does not seem like the intuitive way of representing things. Of course a person has the liberty to arrange the axes in whatever fashion they see fit, but the standard seems to be the way shown above. I wonder who thought it was a good idea to arrange the axes in this fashion, and why they chose to do so.

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    $\begingroup$ Afaik it might be even region-dependent. I think any physicist would say for that, it is just a casual selection and all the coordinate systems are equally valid (more exactly, only half of it due to chirality problems). $\endgroup$ – peterh Apr 30 at 6:07
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    $\begingroup$ It is "quite standard"; see Axonometry. $\endgroup$ – Mauro ALLEGRANZA Apr 30 at 7:55
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    $\begingroup$ I am not sure this is a history question. The alternative arrangement, with x where y is, and y at the opposite of x, is also widely used, especially in Europe. My guess is that the preference for this arrangement comes from the fact that x and y directions are more widely separated, making the figures with additional elements less clogged. $\endgroup$ – Conifold Apr 30 at 8:22
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    $\begingroup$ Just wait until you see the difference between optical raytracing orientation versus aircraft axes orientation! It's all a matter of custom. $\endgroup$ – Carl Witthoft Apr 30 at 12:33

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