1) Let's draw that to better understand this
The Bisector Theorem states that the angle bisected is equally divided
since the angle TRB = 86º . Besides that the m TR
To determine whether it does bisect let's set an equation in which x +27 = the half of 86º
x+27 =43
x=16
3x -5 =43
3x =48
x=16
So, RI bisects the angle TRB, for each angle is half of the measure of TRB.