A triangle has special lines, such as angle bisectors and perpendicular bisector. These special lines are concurrent with their corresponding concurrent points, and called incenter, excenter and circumcenter. This thesis discusses how to compute the radian of Sawayama-Thebault’s circle using trigonometry and area of a triangle, i.e. r1 = (L/a)(1 − βτ )(1 + γτ ) and r2 = (L/aτ 2)(τ + �…