The angle bisector of an angle in a triangle divides the opposite side in the same ratio as the sides adjacent to the angle.
Angle Bisector Theorem
Explore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Angle Bisector Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/AngleBisectorTheorem.html