Author's notes:
#1 Kruemel wrote this little story some time ago to when the teachers made his Mistress study trigonometrical functions. Here is a hint for all readers who are not too familiar with the Muggle equivalent of Arithmancy: y = cos (x – 0.5pi) looks exactly like y = sin x.

#2 Kruemel thanks DD Agent for beta-reading. He is a house-elf from Germany and writing in English is difficult for him.

Disclaimer: This story is based on characters and situations created by the venerable Mrs Joanne Kathleen Rowling. Harry Potter and other trademarks are owned by said Lady and also by various Muggle business people including but not limited to Carlsen Verlag GmbH, Bloomsbury Books and Warner Bros. Inc. No money is being made and no copyright or trademark infringement is intended.
Kruemel owns nothing.

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Harry Potter and the Rescue of the Cosine

By Kruemel

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„Oh, no!" Professor Trelawney cried suddenly. „The Cosine! He-Who-Must-Not-Be-Named is after it. I need to alert the headmaster."

She hardly took the time to dismiss the class before she dashed out of the room.

-

„We can't allow You-Know-Who to take hold of the Cosine," Hermione exclaimed on their way down from the Divination Tower. „We've got to do something!"

„Yes," Harry agreed at once. „But what?"

Ron groaned, „Can't we just let the teachers deal with the problem for a change?"

„I've already got an idea!" Hermione retorted. She set off towards the secret Room of Functions.

The boys followed.

-

In the Room of Functions, Hermione took out her wand. „I will transform the Cosine into an ordinary Sine. Then You-Know-Who can't recognise it."

She performed the spell.

„Err, well..." Harry said uncertainly.

Hermione frowned.

„Looks a bit out of place," Ron muttered.

Hermione's brow wrinkled some more, and she transformed the function back into its original state.

„I know a better way to disguise it!" she declared excitedly. "Ron, fetch me a pair of brackets. We also need a half of a Pi. Harry, you see to that."

Ron obediently took a pair of brackets from the sideboard and prized it open. Harry hastened to measure out a half of a Pi. Hermione meanwhile rummaged through her bag to find a spare minus.

When everything was ready, Hermione put the items into the brackets: first a shiny X, then the minus and finally the half of the Pi, which Harry handed to her. She attempted to close the brackets but they were too heavy for her.

„Let me!" Harry said urgently. „We're wasting time."

He pushed and shoved. He had to put all his weight on the brackets before they, at long last, clicked properly together. It was about time; there were footsteps to be heard.

Harry, Ron and Hermione ran and hid themselves behind the large sculpture of Logarithm the Horrible.

Voldemort stomped into the room. He looked around. „Now, where is this wretched Cosine", he asked under his breath.

Luckily, Hermione's trick worked. No matter how hard he looked, Voldemort couldn't find the Cosine although it was right before him. He even knocked his left toe against it accidentally.

Bloody Sine", he muttered moodily and left.

-

Harry, Ron and Hermione came out of their hiding place.

„Well, I told you we could do it," Hermione said triumphantly. „Let's go now!"

But it was too late. The door opened, and Professor Severus Snape, the potions master, strode into the room.

„What's this?" he asked in his silken voice. „Potter, Weasley and Granger off limits again? This will cost Gryffindor twenty points for each of you."

„But Sir! We rescued the Cosine!"Hermione protested fiercely.

„That means another twenty points off for messing with a valuable Function."

„You know..." Ron cried when hearing this. „You're really, really unfair!"

Snape's lip curled. „Very good, Mr Weasley. I'll take another twenty points off Gryffindor for you having opinions about your Potions teacher. And Potter, what excuse do you have?"

Harry looked like he was going to faint. "N-none, Sir," he stammered.

"Well then, maybe a little detention will give you time to think about it. Be in my office tonight at nine p.m.," Snape said smoothly. "You will be cutting cucumber roots."

- The End -