The Circle

Question 1

How do you determine if a point is on circle?

Answer 1

x^2 + y^2 = r^2

Question 2

How do you determine if a point is inside circle?

Answer 2

x^2 + y^2 < r^2

Question 3

How do you determine if a point is outside circle?

Answer 3

x^2 + y^2 > r^2

Question 4

How do you determine if two circles touch externally?

Answer 4

Distance between centres = r1 + r2

Question 5

How do you determine if two circles touch internally?

Answer 5

Distance between centres = |r1 + r2|