To determine the true energy from a distance, the method of trigonometric functions is used: in a triangle, if two angles and the length of one side are known, then the other side lengths and even the height of the triangle can be calculated.
Before rangefinders came out, or before rangefinders were widely deployed in troops, artillery actually used this method to measure distance:
The 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 make contact by phone and observe the same hostile target from two observation points, and you can measure two angles.
Then, you can use this side and the two angles to accurately calculate the distance to the target, and then use the distance, depression angle, and elevation angle to calculate the target's height.
This requires that all artillery observers must have mental arithmetic skills and be fast.
The reason is that if the target is an enemy artillery group and the enemy and we are engaged in an artillery battle... then we need to calculate the distance and height of the target within a few seconds, and then use the fastest time to accurately hit the enemy's artillery position with the artillery shells.
Just a few seconds of delay could cause a complete rout.
Wang Xuexin does not have such excellent mental arithmetic ability, and in fact, he does not need to have such mental arithmetic ability... The situation he faces is different. The Japanese turret is right there, and it cannot walk or move, and its machine gun has a range of only more than 600 meters.
rice.
The Eighth Route Army could slowly measure and calculate outside the range of the gun towers, and even check the calculations several times.
If you find it troublesome to calculate trigonometric functions for any angle, you can also use special angles.
If it doesn't work, just use the Pythagorean theorem to calculate the entire ninety degrees. It's so easy!
This is what Wang Xuexin taught Laojiu in the wild.
Anyway, they didn't pull the cannon out. They just carried bamboo poles on their backs with Laojiu and his artillerymen in the field, measured them, and then calculated and verified them.
First of all, you have to make a few protractors... This thing is not difficult to make, you just need to be patient: a straight angle is one hundred and eighty degrees, and each square divided into eighteen equal parts is ten degrees, and each square is divided into ten equal parts, and one degree comes out.
Then insert the pole, measure the length of one side and add two angles, and quickly calculate the distance.
Laojiu didn't believe it at first, but when I measured it with a cloth ruler, it was right.
I randomly changed positions and tried several times, but the result was still the same.
Wang Xuexin even found a clever way to draw a similar triangle on paper: for example, if a measurable side is 100 meters, draw a 10 cm line segment on the paper, and then draw a triangle from the two angles.
.
Now you don't need any trigonometric functions or anything like that. You just need to use a ruler to measure the length on the paper and then enlarge it proportionally.
This tricky approach will inevitably have some errors, because there is a deviation in the measurement on the paper, and then when enlarging it to the same proportion, the deviation will also be magnified ten thousand times.
However, for the Eighth Route Army who have not systematically studied mathematics and trigonometric functions, this clever method is very suitable for them to roughly calculate the distance as quickly as possible.
However, Wang Xuexin still underestimated the ability of Lao Jiu and other first-class soldiers...
They were overjoyed when they discovered this method. They including Laojiu wanted to worship Wang Xuexin as their teacher on the spot... In this era, there was still a practice of learning skills from a teacher. They thought this was Wang Xuexin's craft, a low-end technology that was not spread to outsiders.
unique skill.
Laojiu thought to himself, if there is no master-disciple relationship, why should someone teach you this skill?
Of course Wang Xuexin didn't dare to accept it.
Just kidding, Laojiu is already a veteran in the army. All the soldiers in the independent regiment call him "Uncle Jiu". How dare Wang Xuexin accept him as his apprentice.
"Uncle Jiu!" Wang Xuexin quickly stopped Lao Jiu and said, "This is nothing, it's not a craft. We are all revolutionary comrades, and we are all here to fight the Japanese, so don't be so open-minded!"
Laojiu retorted: "What kind of alienation is this? There is no discipline in our army that prohibits apprenticeships. Look at the hoemaker Lao Zhang. Didn't he just accept two apprentices? And the bamboo basket weaving Lao Zhao
, he also collected four or five!”
Other artillerymen also said one by one:
"That's right, Comrade Wang Xuexin! It's not against discipline to accept a disciple!"
"Not only did it not violate it, the superiors even promoted it!"
"This skill of yours is very important to our artillery. You need to learn it so that you can hit the Japanese with accuracy every time!"
"Yes, the 50 cannon can also be used!"
…
Wang Xuexin tried to talk a lot, but in the end he couldn't give up. He said he wanted to become a disciple and stopped teaching. Only then did the old wine and others give up.
Then Wang Xuexin started teaching that night.
It only talks about two big parts: one is the parabola and the other is the trigonometric function.
Then we won’t talk about any principles, theorems or the like.
If we really wanted to talk about this, we would have to go back and teach junior high school physics and mathematics one by one.
What Wang Xuexin talked about was the work formula, asking everyone to memorize it, and then put which number where, and then put it where after the number was calculated. It just came out after a mechanical application.
Wang Xuexin originally thought it would be good if one or two of the dozens of artillerymen could learn how to do it.
As a result, on the next day, Wang Xuexin was surprised to find that half of them, who had no foundation in mathematics or physics, could actually calculate, and some of them could calculate quite quickly.
Wang Xuexin believes that this is because the calculation method is the same and the process is the same. The only thing that changes is the number. You can remember it after calculating it several times.
On the other hand, it is the threat of war that stimulates their potential... As long as they can learn to calculate correctly, they can fight the Japanese! Of course they have to study hard.
This is indeed the case. These artillerymen stayed up all night last night, all writing and calculating with kerosene lamps on.
When Li Yunlong came to inspect, he felt strange when he saw the brightly lit barracks of the artillery unit. He asked, "What are you so crazy about? Are you writing and drawing here in the middle of the night, writing a review or something?"
Laojiu came up and explained: "Captain, didn't you ask us to think about the 'Ghost Cannon' thoroughly? Aren't we busy right now?"
"Play the piano randomly!" Li Yunlong scolded angrily: "I obviously asked you to practice more, that is, I asked you to practice cannon. How about you practice writing for me? Can this thing be used as a cannon? Who can I learn from?
Isn’t it time to imitate the political commissar?”
"Captain!" 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 Xiao Dongbei! In short, I promise that I will hit wherever you point me.
Never hold back the troops! Just don’t care what we do!"
When Li Yunlong heard this, he realized that what Laojiu said was true. He was an amateur when it came to artillery, and it might be bad to interfere randomly.
What's more, this is taught by Xiao Dongbei...it's still a secret technique, so maybe it's really reliable?