“Hum?” After walking into the library, Yun Xi found that the library wasn’t small at all.

Looking at it from the outside, it was just a three-story wooden house, but its inside was incredibly wide.

“Is its inner space expanded by magic?” Looking at the over ten-story spiral staircase and the aisles amongst one bookshelf after another, it couldn’t be just a three-story house.

Moreover, there was a light curtain covering the entrance of the basement, which meant that there was a wide space under the ground too.

Yun Xi drew out the shell and touched the light curtain, just like what happened when he touched the magic circle of the girl’s dorm, this light curtain straightly disappeared. Apparently, the Sky Sword’s token could be used here too.

However, he wasn’t going to go to the basement now. He was just looking for some beginner books.

Geography, astronomy, history... math! Yun Xi found the books he needed on the third floor.

The beginner books to learn Yun Hai’s Quadrant Sword were just some basic math books.

However, don’t look down on them. They were the cornerstones of math, the base of calculating.

“Well, let me borrow more books.” After finding “Nine Chapters on Mathematical Art” and “Geometrical Principle”, Yun Xi picked up several other books on the bookshelf.

“Probability Calculus.”

“Introduction to Calculus – Even a Monkey can Understand it!”

“Theory of Real Number.”

The five beginner books were what Yun Xi was going to read as the introduction to mathematics.

After picking up the five books, he looked at the books on the top of the bookshelf. Immediately, he felt that he might be a monkey, because he didn’t understand the titles of the books at all.

“Is the Cat Dead or Alive?”

“I Will Kill that Damned Cat!”

“The Ghost Cat of Mathematics, Two Theories about the Question of Yun Hai the Sky Sword.”

“36 Proof Techniques to Verify if the Cat is Dead or Alive.”

“It’s Wrong to Torment the Cat!”

“I Will Eat that Cat!”

“I Don’t Believe this Theory! I Prefer to Believe that Cats never Exist in this World!”

“Yun Hai, F**k You and Your Cat!”

A pile of books all referred to a mysterious cat. Looking at the names of the authors on the books, Yun Xi found almost all the names of the top mathematicians he knew, including a dragon, and someone was directly cursing Yun Hai the Sky Sword in the title.

It seemed that all the mathematicians all over the world were in a towering rage when referring to the cat.

“It must be a very strong cat!” Yun Xi thought. It seemed that Yun Hai was the first person who put forward the theory about the cat.

He had a feeling that if he wanted to master Yun Hai’s Quadrant Sword, he would have to face that cat sooner or later.

...

Deep In the night, Yun Xi lay on his bed with a painful look.

“It’s too difficult to understand the content of the books! Are they really just the basic knowledge to learn Yun Hai’s Quadrant Sword?” Yun Xi didn’t expect that it was so hard to study mathematics!

He just read “Nine Chapters on Mathematical Art” and “Geometrical Principle”, and they had made him fall into the endless computation of infinite loops.

Because he was already a hero ranked Baker, his strong hero ranked mentality helped him a lot.

At the hero rank, his computation speed was hundreds of times faster than ordinary people. He could calculate Pi to hundreds of decimal places and instinctively kept calculating.

To ordinary people, it wouldn’t be a problem because humans would instinctively give up thinking about the thing that was beyond their computing power. But to Yun Xi, he just couldn’t turn a blind eye to the formulas!

What’s the limiting value of this angle? What’s the threshold of this unknown number? Why did the computation fall into an infinite loop?

Before he went to the sword palace, he only learned add, subtract, multiply and divide because he needed to record the income of his family’s bread shop every day. The four fundamental operations of arithmetic were sufficient for him at that time.

After studying the knowledge in “Nine Chapters on Mathematical Art” and “Geometrical Principle”, he finally understood how hard the real mathematics was.

It was a “Tao” that could explain everything in the universe. “Mathematics” didn’t stand for truth, because it was a process that was used to pursue the truth of the universe.

From mathematics, people could sum up the nature of astronomy, physics and even the world itself. It was a wisdom that applied to every place in the entire god’s domains, which was sufficient to be the core of the godlike sword skill, Yun Hai’s Quadrant Sword.

“How did Yun Hai create his sword skill by using math? It makes no sense!” Yun Xi only felt awe about Yun Hai’s wisdom.

He was sure that Yun Hai’s Quadrant Sword wasn’t possible to be mastered by ordinary people, because only the best geniuses of math could learn its basics after endless failures.

Compared to Hua Huo’s Sky Flying Sword, Yun Hai’s Quadrant Sword seemed to be easy to study, however, it was actually more difficult than any sword skill Yun Xi had ever known.

It seemed that everyone could learn the basics of Yun Hai’s Quadrant Sword by reading “Nine Chapters on Mathematical Art” and “Geometrical Principle”, unfortunately, it was just a delusion.

Even Yun Xi, whose computation speed was hundreds of times faster than ordinary people, felt the strain of learning the basics of Yun Hai’s Quadrant Sword, not to mention other people. Perhaps Yun Hai was a real super genius of math, just like Hua Huo was a super genius of sword.

“No, I should stop calculating!” Yun Xi pressed his hands on his head. It wasn’t a sword skill he could learn now. He even doubted that Yun Hai’s understanding about math had entered the legend rank when he created this sword skill.

Only super geniuses of math could learn the basic of Yun Hai’s Quadrant Sword, as for when could they master it? Only god knows.

“Nah, forget it. Let’s me try Teacher Casina’s gift first.” With a sad look upon his face, Yun Hai touched the shell in front of his chest and gave the words.

“Open for me, the Sky Tower!”

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