Da Ming: The system granted me immortality; I clock in every day.

Hu Guang almost burst into tears when he got to this point.

Although the Imperial Astronomical Bureau in the early Ming Dynasty had a Hui (Muslim) section, due to the wars, the experts who were proficient in the Western Regions calendar had long since died out.

Faced with that profound book of Persian astronomy and mathematics.

These learned scholars, well-versed in the Four Books and Five Classics, were completely baffled, as if reading a book written in a foreign language.

If it cannot be solved within three days, it will be a disgrace to the Ming Dynasty.

Emperor Yongle (Zhu Di)'s murderous blade would undoubtedly fall mercilessly onto their necks.

"I see."

Gu Yannian opened the heavy iron door of the Class A library and stepped aside to let everyone in.

"The astrological, calendrical, and mathematical classics left over from the previous Yuan dynasty are all on the third to fifth rows of bookshelves here. Please make yourselves at home."

After saying that, Gu Yannian stepped aside and stood by with his hands in his sleeves.

Hu Guang and the supervisor immediately directed the accompanying officials to rush towards the bookshelf like hungry tigers pouncing on their prey.

They started frantically searching.

Dust filled the library in an instant.

The dull thud of books falling mingled with the anxious sighs of the officials.

They turned Gu Yannian's beloved peaceful place into a chaotic mess.

Gu Yannian returned to his desk on the second floor and poured himself another cup of tea.

He listened to the commotion downstairs, but his heart remained unmoved.

The astronomical calendars of the Western Regions, in their origins, largely blended ancient Greek Ptolemaic astronomy with Arabic spherical trigonometry.

This so-called "arc-arrow calculation array" is seen by scholars of the Ming Dynasty as divine pronouncements.

But in the eyes of Gu Yannian, who came from modern Earth, it was nothing more than spherical geometry and trigonometric functions in basic mathematics from high school to university.

Time passed by, second by second.

For two whole days, the library became a bustling vegetable market.

The officials of the Imperial Observatory wore out countless ancient books.

Yet he was still at a loss when faced with the Persian arithmetic diagram he had copied.

Hu Guang's lips were blistered from the stress, and several veteran mathematics officials were so exhausted that their eyes were bloodshot and they were almost fainting.

On the morning of the third day, the atmosphere inside the library was extremely oppressive.

The shadow of death has already loomed over these officials.

If there is no result by noon today, they will have to go to the palace to be punished.

"Heaven has forsaken me! This barbaric and cunning method of calculation is completely contrary to the principles of the Zhoubi Suanjing (周髸经), the mathematical classic of our Chinese civilization. How can one possibly draw a tangent in the air on this arc to determine the distance of the stars!"

The supervisor slammed an ancient book to the ground.

Tears streamed down his face; he had already resolved to die.

On the second floor, Gu Yannian was carefully wiping an ancient inkstone with a clean silk cloth.

He lowered his eyes slightly, listening to the wails downstairs, and sighed inwardly.

If he lets this group of people cry and wail here, he'll probably be unable to stay in the Bureau of Justice from now on.

Moreover, if these officials were beheaded by Zhu Di, the Crown Prince's palace would inevitably be implicated.

At that time, Crown Prince Zhu Gaochi will surely be upset.

They might come to him to complain again, causing endless trouble.

Those who achieve immortality do not actively participate in the game.

However, in order to maintain a comfortable living environment, it is absolutely necessary to occasionally and discreetly clear away some obstacles.

Gu Yannian put down the silk cloth and slowly walked down the stairs.

He carried a plate of freshly sliced ​​autumn pears to a large desk where Hu Guang and the supervisor were sitting, and gently placed the fruit plate down.

"You gentlemen have been working hard these past few days, have a piece of pear to soothe your throats."

Gu Yannian's expression was gentle, but his gaze naturally fell on the Persian drawing spread out on the table.

The drawing was filled with intricate concentric circles and intersecting arcs, with winding Persian numbers and symbols marked on the side.

To outsiders, it was nothing short of scribbles.

But under Gu Yannian's insight, every symbol on the drawing instantly transformed into clear Arabic numerals and modern trigonometric formulas in his mind.

Sine, cosine, tangent.

The so-called "incomplete formula" is nothing more than knowing two elements of a spherical right triangle and trying to find the length of another arc.

This is the procedure used to accurately calculate the angle between the ecliptic and the equator.

too easy.

It's so simple it's practically an insult to Gu Yannian's intelligence.

He doesn't even need to write anything; the immense computing power in his mind is available in a fraction of a second.

That's how we got that precise data.

"Gu Xima is very thoughtful."

Hu Guang waved his hand wearily, unable to eat the pear.

"My head is almost out of my hands. This Persian's calculation is simply unsolvable."

Gu Yannian didn't say much, but simply bowed slightly and retreated to the depths of the bookshelf.

He walked to a corner piled with tattered old manuscripts from the Yuan Dynasty and casually pulled out a yellowed piece of mulberry paper.

He did not use the wolf-hair brush commonly used by the Bureau of Justice.

Instead, he took out an ordinary charcoal pencil from his sleeve.

This charcoal pencil was something he made himself to quickly record book titles.

The lines drawn are similar to those written with a hard pen in the ancient Western Regions.

Gu Yannian leaned against the bookshelf, his eyes calm and still.

He quickly completed the derivation of the formula on mulberry paper, using standard Arabic numerals commonly used in the pre-eocene Islamic world, and wrote down the final result.

To avoid appearing abrupt, he deliberately used very light ink to write the eight characters "弧矢割圈，借径求弦" in Chinese next to it.

The font is crudely and archaic, resembling the scribbles of a down-on-his-luck calendar judge from a century ago.

After he finished writing, he crumpled the mulberry paper a few times.

This made it look even older, and then I casually tucked it into a thick book called "The Great Yuan Calendar".

After doing all this, Gu Yannian picked up a basin of water and walked to the desk where Hu Guang and the others were.

"You gentlemen have been studying here for many days, and your desks are quite dusty. Let me wipe them clean for you."

As Gu Yannian spoke, he naturally moved the book "Da Yuan Li Li" (The Great Yuan Calendar) with mulberry paper tucked inside from the cart to the supervisor's side.

He moved gently, but his wrist twitched slightly the instant he put the book down.

The yellowed mulberry paper happened to slip from the pages of the book and landed lightly on top of the Persian drawing.

The supervisor was closing his eyes and waiting for death when he suddenly felt something fall in front of him.

He subconsciously opened his eyes, his gaze falling on the mulberry bark paper.

At first, he didn't care.

But when he saw clearly the drawings and the curved numerical symbols on the paper, he realized they were similar to the drawings brought by the Persian envoy.

His pupils contracted to their maximum size instantly.

"What...what is this?!"

The supervisor sat up abruptly and grabbed the mulberry bark paper.

Hu Guang was also startled and leaned closer.

Several senior scholars from the Imperial Observatory's Hui (Muslim) department immediately surrounded them.

Although they couldn't calculate the complex derivations, they recognized these basic Western Region numbers.

"Heavens! This...this is a divination manuscript left behind by a master from the Yuan Dynasty!"

An old scholar was so excited that he trembled all over as he pointed at the Chinese characters on the mulberry paper.

"An arc bisects a circle, using a path to find the chord! Yes! We've been fixated on the Pythagorean theorem on a plane, forgetting that the starry dome is an arc!"

"This predecessor from a hundred years ago had already solved such an unparalleled divination formation!"

"Quickly! Compare this result with the Persian drawings!"

As if injected with a stimulant, Jian Zheng roared wildly.

A group of people immediately pounced on the table.

Following the derivation steps on the mulberry paper and combining them with the existing calendar data of the Ming Dynasty, they began the intense process of reverse calculation.