DD209 Running The Economy : Very odd way to describe a 45 degree line.

This is beginning to feel like I'm just complaining now about the little things, but 'Economics' is difficult enough without reading explanations of things I know that I know, that then confuse me.

Modelling Planned saving (1) tutorial says the following....

"So let’s start with just the two scaled axes and imagine that each value of income emits a ray of light vertically. 

A mirror is held diagonally to reflect that ray on to the vertical axis. 

Click on each circle on the bar underneath the chart, working from left to right to watch this process build up step by step."

 I could not understand what this meant, or what it was supposed to achieve, or how this related to economics.

So you hold a mirror diagonally, but at what angle, obviously the angle of reflection is absolutely critical when reflecting the light, an angle of 30 degrees will reflect the light on to the vertical axis at a very different point to an angle of 60 degrees.

I was pretty confused as to where this was going, there didn't seem to be anything about this in the text book.

So I clicked and moved the circle as directed and the angle of the mirror (that was set by the application) was at 45 degrees (although it never mentions this), therefore a vertical light shone from horizontal value 10 would be reflected to vertical value 10, and horizontal 20 to vertical 20, and so a line of 45 degrees is drawn in front of you.

However to get to this explanation of how you come to draw a line of 45 degrees, you sort of have to understand the mirror is already at 45 degrees, but 'mirror imaged' so really 180 degrees away from your 45 degree line. This just appears to me to be a nonsense explanation, you have to understand the mirror is at 45 degrees in order to draw a line of 45 degrees, so the answer is part of the explanation - how does that work, its like the argument "god made the world so perfect so that proves god exists" - eh ? what ? no it doesn't.

So for me, this explanation just confuses things that are basic maths and nothing at all to do with economics.

On the plus side - the rest of the tutorial is really good ! Really, really, good !!

So, Week 4 complete, bring on Chapter 4 and Fiscal Policy. I guess there is going to be even more sums to be done, and I hope I may even begin to enjoy economics.