Hello, thamathkid1729!

Angle FAB is 45 degrees; angle FCB is 45 degrees.

But the angle between the two triangles is **not** 45 degrees.

Look at it this way . . .

We have a cube (labeled ABCDEFGH).

Using a sharp knife, cut straight through vertices A, C, and F.

Remove the upper (larger) potion of the cube.

We will have a "corner" of the cube.

Code:

F *
|* *
| * *
| * *
| * *
| * *
| * * A
| * *
| * *
| * *
B *---------*
C

We want the angle between the slanted face and the "floor".

earboth has the best plan for this.