# Circles

### Example 1

How is it possible for two circles to have only two common tangents?

### Example 2

How is it possible for two circles to have only one common tangent?

### Example 3

A diameter is a secant. True or false?

### Example 4

If a line *m* is perpendicular to the radius of a circle, then *m *is not a secant of the circle. True or false?

### Example 5

In the figure below, segments *PB* and *PA* are tangent to ⊙*O* at *B* and *A*, respectively. Also, ∠*AOB* is a right angle. Prove that ∠*APB* is a right angle.