You are confusing between a definition and description of a phenomenon and the formula/equation used to calculate the effect of such a phenomenon.

What I gave is a description of return in Mie region. To calculate the effect then you have to use equation and formula. To apply in the real world you normally need a computer to do the calculation for you.

For example: If the task is to make a plane fly.

The description would be: to generate more lift than the mass of the airplane.

The equation would be: Lift = 1/2*air density*lift coefficient* velocity^2* reference wing area.

The practical design would be: using wind tunnel to measure lift coefficient of different shape and their structural strength.

Similarly, the description I cited are the general guidance to how you should design a stealth aircraft: avoid corner, avoid sharp edges, avoid gaps ..etc. But to know what is the most optimum way to do them, you need a computer, because even though you have the equation and you have the theory, doing the thounsands-millions calculation is not the task that anyone really wants to do.

This is the reason why a very strong mathematical background required for any complicated engineering design.

This is the same case like in the Quantum chromodynamics and the Quantum electrodynamics .

The centre of gravity / lift can be calculated with the general knowledge of the shape, after this calculation the centre of gravity / lift will not move too much if you consider the exacts shape of edges, holes protrusions and so on.

With the interaction of the electromagnetic field with the body of the aircraft the mathematical method and model is different,

If you add a small detail to the model then the backscatter to the emitter will change not by the relative magnitude of the change, like in the case of centre of lift, but by the same magnitude like with the first calculation .

See ?

So , all simplified model will be useless for the design.

Of course I know aircraft have different radar scattering characteristic in vertical and horizontal polarization, the graph I posted in the previous post literally shown that.

Besides, you are mistaken, only return in optical region (high frequency radar) can be independent of the frequency, whereas return in Mie and Rayleigh region (low frequency radar) is always dependent on frequency.

Again, check the results of real life experiments.

This is a bit more complex than this simplified model.

Yes the nose of Su-34 is not a cylinder, so that help prevent creeping wave return, however, apart from that tiny detail, Su-34 does nothing to reduce specular and creeping wave return, like I said before: has external weapons (keep in mind most missiles and bombs has cylinder shape), a straight inlet with exposed turbine blades, straight up vertical stabilizer making 90 degrees angle with the fuselage, pylons making 90 degrees corner with the wing, rectangle inlet with 90 degrees angle, the 2 inlets also make another right angle corner with the fuselage, the radar aperture is vertical, the trailing and leading edges have no edge treatment. In other words, the nose of su-34 is the equivalent of putting lipstick on a pig or putting V-tail on B-52. It won't make su-34 stealthy in any shape or form.

The Russians did a deep and expensive work with the robot applied lamination of the air intakes and so on.

So , two possible motivation :

1. Russians are stupid, and did a pointless work

2. The X band backscatter satisfy the military requirements.

Considering that the Russians has no issue to refuse the delivery of a military hardware it the performance of it doesn't hit the requirements (it is the opposite of the USA practice) we have to consider that maybe the explanation #2 is true.

Of course it gives only frontal low observation characteristic, and it can be slightly bigger in X band than the F-35, but the Su-34 has to penetrate a patriot battery, not an S-300, and even a flying pig with a lipstick can do that : P