# daily puzzle

Started by September 14, 2020
```A quickie.  No diagram, but no need.

Given a unit cube, vertices labeled ABCD on the top face,
EFGH on the bottom;  where A <-->  E,  B <--> F,  etc.
Draw diagonals GD and BD,  across the appropriate faces.

What is the angle GDB?

You have two minutes, no calculator, pen and paper only -

--
Rich
```
```On Monday, September 14, 2020 at 2:49:51 PM UTC-7, RichD wrote:
> A quickie. No diagram, but no need.
>
> Given a unit cube, vertices labeled ABCD on the top face,
> EFGH on the bottom; where A <--> E, B <--> F, etc.
> Draw diagonals GD and BD, across the appropriate faces.
>
> What is the angle GDB?

Maybe closer to the subject of this group, what is the symmetry of
the 111 face of a silicon crystal.  (Or any cubic crystal.)

With the right coordinate system, the coordinates of the points
in question are , , and .

However, the answer is even easier, as there is only one angle
that is a possible solution, and that we should know without the
need to look it up.
```
```On Tuesday, September 15, 2020 at 6:49:51 AM UTC+9, RichD wrote:
> A quickie. No diagram, but no need.
>
> Given a unit cube, vertices labeled ABCD on the top face,
> EFGH on the bottom; where A <--> E, B <--> F, etc.
> Draw diagonals GD and BD, across the appropriate faces.
>
> What is the angle GDB?
>
> You have two minutes, no calculator, pen and paper only -
>
> --
> Rich
60 deg?
```