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a) |
If two circles touch externally, the distance between their centres is the sum of their radii. |
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b) |
If two circles touch externally, their centres and the point of contact form an isosceles triangle. |
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c) |
If two circles touch internally, their centres and the point of contact form a scalene triangle. |
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d) |
If two circles touch internally, the distance between their centres is the difference of their radii. |
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e) |
If two circles touch internally, the square of the distance between their centres is the difference of the squares of their radii. |
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f) |
If two circles touch externally, the square of the distance between their centres is the sum of the squares of their radii. |