Bright Sword Military System

The method of trigonometric functions is used: in a triangle, if two angles and one side length are known, then the other side lengths and even the height of the triangle can be calculated.

Before the range finder came out, or before the range finder was equipped with a large number of troops, the artillery actually used this method to measure range:

Two teams of artillery observers set up two observation points at a certain distance along the defense line. The distance between the two observation points is measurable, which is a known side of the triangle.

Then use the telephone to observe the same hostile target from two observation points, and then two angles can be measured.

Then, you can use this side and two angles to accurately calculate the distance to the target, and then calculate the height of the target from the distance, depression angle, and elevation angle.

This requires all artillery observers to have mental arithmetic ability, and to be fast.

The reason is that if the target is the enemy's artillery group, the enemy and us are engaged in artillery battle... At this time, the distance and height of the target must be calculated within a few seconds, and then the artillery shells will be accurately dropped into the enemy's artillery positions in the fastest time.

Just a few seconds of slowness can cause total rout.

Wang Xuexin didn't have such excellent mental arithmetic ability, and actually didn't need to have such mental arithmetic ability... The situation he faced was different. The devil's gun tower was there, he couldn't walk or move, and his machine gun had a range of only more than 600 meters.

The Eighth Route Army can measure and calculate slowly outside the range of the gun tower, and even check the calculation several times.

If you think the trigonometric functions of arbitrary angles are troublesome, you can also take special angles.

If it doesn’t work, use the Pythagorean theorem to calculate the whole [-] degrees, it’s so simple!

This is what Wang Xuexin taught Lao Jiu in the field.

Anyway, he didn't pull the cannon out, but carried a bamboo pole with Laojiu and his artillerymen in the field to measure it, and then counted and verified it.

First of all, you need to make some protractors... It is not difficult to make this thing, but you need a little patience: the flat angle is 180 degrees, and each division of eighteen equal divisions is ten degrees, and each division is divided into ten equal divisions, and it will come out at one degree.

Then, as soon as the pole is inserted, measure the length of one side and the two corners, and quickly calculate the distance.

Laojiu didn't believe it at first, but he measured it with a cloth ruler, and it was not bad at all.

Randomly switched positions and tried a few more times, same result.

Wang Xuexin even found a tricky way to draw a similar triangle on paper: for example, if a measurable side is 100 meters, draw a line segment of 10 cm on the paper, and then draw a triangle when two angles are drawn .

In this way, there is no need for trigonometric functions and the like, just use a ruler to measure the length on the paper and scale it up proportionally.

This tricky approach will inevitably have some errors, because there is a deviation in the amount on paper, and then the deviation will be magnified ten thousand times when it is scaled up.

However, for the Eighth Route Army who have not systematically studied mathematics and trigonometric functions, this kind of tricky method is very suitable for them to roughly calculate the distance at the fastest speed.

However, Wang Xuexin still underestimated the ability of Lao Jiu and other soldiers...

They were overjoyed when they discovered this method, and they wanted to worship Wang Xuexin as their teacher on the spot, including Laojiu... In this era, there is still such a thing as apprenticeship and learning skills. They think this is Wang Xuexin's craftsmanship, a bottom-of-the-box technique, and it is not rumored. unique skill.

Lao Jiu thought to himself, if you don't have a teacher-student relationship, why would someone teach you this skill?

Of course Wang Xuexin didn't dare to accept it.

Just kidding, Lao Jiu is also a veteran in the army, and all the soldiers in the independent regiment call him "Uncle Jiu", how dare Wang Xuexin accept him as an apprentice.

"Uncle Jiu!" Wang Xuexin hurriedly stopped Lao Jiu, and said, "It's nothing, it's not a craft, we are all revolutionary comrades, and we all want to beat devils, so don't be so alien!"

Laojiu retorted: "What's wrong with this? There is no discipline in our army that says you can't apprentice. Look at that old Zhang who made a hoe, didn't he just accept two apprentices? And that old Zhao who weaves bamboo baskets , He also collected four or five!"

The other artillerymen also said one by one:

"That's right, Comrade Wang Xuexin! Accepting apprentices is not a violation of discipline!"

"Not only is it not violated, but the superior also advocates it!"

"Your skill is very important to us artillerymen. You have to learn it. When you fight devils, you are sure to hit every shot!"

"Yes, the [-] cannon can also be used!"

……

Wang Xuexin talked all kinds of things, but in the end he couldn't do it. He said that he would not teach if he wanted to be a teacher.

Then Wang Xuexin started a class that night.

There are two big parts: one is parabola and the other is trigonometric functions.

Then I don’t talk about principles, theorems, and the like.

If this is true, then one by one, one has to go back and talk about both junior high school physics and mathematics.

What Wang Xuexin talked about was the working formula, so that everyone should memorize it, and then put which number, and where to put the number after it is calculated, so that it will come out after rote.

Wang Xuexin originally thought that it would be good if one or two of the dozens of artillerymen could learn it.

As a result, on the second day, Wang Xuexin was surprised to find that half of them who had no foundation in mathematics and physics could do the math, and some of them could do it quite quickly.

Wang Xuexin believes that this is because the calculation methods are the same and the process is the same. The only thing that changes is the number, which can be recorded after several calculations.

On the other hand, it is the threat of war that stimulates their potential... As long as they can learn to count correctly, they can beat devils!Of course you have to study hard.

This is indeed the case. These artillerymen stayed up all night last night, and they all wrote with kerosene lamps.

When Li Yunlong came to inspect, he was surprised to see the bright lights in the barracks of the artillery unit, and asked, "What are you guys getting so crazy about? You write and draw here in the middle of the night, what's the matter with writing a review?"

Lao Jiu came up and explained: "Head, didn't you let us figure out the 'ghost cannon'? Aren't we busy?"

"Playing the piano randomly!" Li Yunlong said angrily: "I obviously want you to practice more, that is to let you practice cannons, you are good, practice pens for me? Can this thing be used as a cannon? Who can you learn from?" Is it not easy to learn from the political commissar?"

"Leader!" Laojiu replied: "If you don't understand, just leave it alone, okay? This is not taught by the political commissar, it is the secret technique learned by Xiaodongbei! In short, I promise that in the future, I will fight wherever you point, Never hold back the troops! Don't worry about how we toss!"

When Li Yunlong heard it, what Lao Jiu said was true. He is a layman in the field of guns, and meddling indiscriminately may cause bad things.

What's more, this was taught by Xiao Dongbei... or a secret technique, so maybe it's really reliable?

So I didn't say much.