An excircle is a circle that touches exactly one point of two extended sides of a triangle and the side of the triangle that is facing the circle. This means that the excircle is tangent to the two extended sides and to the side of the triangle that is facing the circle. The excenter is the center of the excircle. Each triangle has three excircles and three excenters.
The bolded green lines are the two extended sides of the triangle. The red line is the side of the triangle that is facing the circle. Instructions for creating excircle Step 1 - create a triangle Step 2- extend two sides of the triangle ( Green lines)\ Step 3- draw a cirlce that is tangent to the side of the triangle that is not extended (The red line) and to the extended lines. ( The green ones)