The process of solving a trapezoidal math problem in junior high school! ! !

This question is very simple, the side length is 4CM? AC=4√2CM？ 4√2-4

Do FN⊥AC in n

∵? The bisector of BAC intersects BD at point E and BC at point F.

What about FB⊥AB? FN⊥AC

∴? FB=FN

Because? The area of △ABC is equal to S△ABF+S△AFC.

So there is? S△ABC=S△ABF+S△AFC

= 1/2? *AB？ *FB？ + 1/2? *AC？ *FN

Easy to get: FB=FN=4√2-4.

There are many ways to prove it, so we should pay attention to the known conditions of rational use of angular bisector.