When two shapes meet at only one point they are TANGENT.

To draw tangencies we must know the folloing rules: 

• FIRST THEOREM: 

A straight line is tangent to a circumference if: 

• • There is a single point of contact (T)

  • The straight line is perpendicular to the radius in T

• SECOND THEOREM: 

A circumference tangent to two straight lines that meet has its center on the bisector of the angle formed by the straight lines.

• THIRD THEOREM: 

Two circumferences are tangent if they have an only point of contact on a straight line that joins the centers.