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# How to show two circles are touching watch

1. (Original post by Felix Felicis)
I wouldn't think you'd need simultaneous equations to show 2 circles touch - if you were asked to find the point of intersection of the two circles then you'd need to use simultaneous equations
But if the two circles interact, doesn't that mean they touch?
2. (Original post by ETRC)
But if the two circles interact, doesn't that mean they touch?
what do you mean by interact
3. (Original post by Farhan.Hanif93)
Simultaneous equations are not a good way to go here; it really pays to think of it geometrically. If you can show that the distance between the two centres is equal to the sum of the radii then you'd be done - think about why i.e. how large would the distance between the centres be if the circles overlapped? How large would that distance be if the circles didn't intersect? What happens in the event that they touch?
And don't forget that one circle may be inside the other, so the distance between the two centres may be the difference between the 2 radii.
4. (Original post by TenOfThem)
what do you mean by interact
Probably meant intersect?
5. (Original post by TheGrinningSkull)
Probably meant intersect?
Probably
6. (Original post by ETRC)
But if the two circles interact, doesn't that mean they touch?
Yes but I meant that you don't need simultaneous equations to just show that they touch

You would need them to actually find the point of intersection
7. (Original post by TenOfThem)
Very true Felix

It is so long since my degree that I am limited to what I teach

Anything beyond M2, S2 (S1 if I am honest) and I am stuck

I can find my way around most of the core

But there are far better than me on here

I start every new A Level group by pointing out that there will be people in the class better at maths than me .... I just have a lot more experience in "spotting"
Compared to most of society, you are very good at maths.

If you don't mind me asking, what uni did you go to?
Compared to most of society, you are very good at maths.

If you don't mind me asking, what uni did you go to?
Manchester
9. (Original post by TenOfThem)
Manchester
aww I want to go there!!

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