A[i][color=#0000ff] common tangent[/color][/i] is a line that is tangent to two circles. All of the lines shown in the figure above are common tangents.[br][br]Do two circles always have to have four common tangents?[br]Time to experiment.[br]Move points A,B,C, and D on the circle and observe the common tangent lines.
Is it possible to have zero common tangents between two circles?[br]Explain your thinking.
Is it possible to have exactly one common tangent line between two circle?[br]Explain your thinking.
What is the maximum number of common tangent lines two circles could have?