Answer:
moon disappear because of the rotation
The number of cycles of a periodic wave per unit time is called the wave's "frequency". The height at which the peaks of the waves reside is the "amplitude".
To minimize the material usage we have to have the volume requested with the minimum surface area.
The volume is:

And the surface is:

From the first equation we get:

I will use k instead of a number just for the conveince.
We plug this into the second equation and we get:

To find the minimum of this function we have to find the zeros of its first derivative.
Sx will denote the first derivative with respect to x and Sy will denote the first derivative with respect to Sy.

Now let both derivatives go to zero and solve the system (this will give us the so-called critical points).

Now we plug in the first equation into the other and we get:

Now we can calculate y:

And finaly we calculate z:

And finaly let's check our result:
Answer:
The spacing between the planes of the crystal is 0.295 nm
Explanation:
Given:
λ = wavelength = 0.24 nm
θ = angle of incidence = 66°
The spacing d between the planes of the crystal is equal:
