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Perpendicularism between line and plane
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Perpendicularism between line and plane

A line r is perpendicular to a plane if, and only if, r is perpendicular to all the lines passing through the intersection point of r e. Note that if a line r is perpendicular to a plane, then it is perpendicular or orthogonal to the entire line of: for a line r to be perpendicular to a plane, it is sufficient to be perpendicular to two competing lines, contained in: below, why it is not enough that r is perpendicular to a single line t of to be perpendicular to the plane: Next: Relative positions of two planes

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What is the largest known prime number?

The largest known prime number is 2 32,582,657 -1, which has 9,808,358 digits and was discovered on 9/4/2006 by Drs. Curtis Cooper, Steven Boone and their team. This cousin has 650,000 digits more than the largest cousin they found in December 2005. How many decimal places of the number Pi are known?
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Why is a suit called a suit?

Suit, referring to clothing, referred to the set of three pieces: pants, jacket and vest. For this reason it is called suit. However, today it is made up of two pieces: pants and suit jacket. What is Sudoku? Index Next >> Number Three and Proverbs
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Guessing a Date of Birth

Ask someone to think about the month number of your birth (January 1, February 2, March 3…). Then ask him to: 1) multiply the number by 2 2) add 5 to the result 3) multiply by 50 4) add your age to the result After the person tells you the result, you must subtract 250. The last two numbers of the end result will give the age of the person while the first number (or first numbers) will be the month of birth.
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Multiplication of 37 by multiples of 3

When we multiply 37 by multiples of 3 less than 30, we come across a curious fact: 3 x 37 = 111 6 x 37 = 222 9 x 37 = 333 12 x 37 = 444 15 x 37 = 555 18 x 37 = 666 21 x 37 = 777 24 x 37 = 888 27 x 37 = 999 Who discovered the Pythagorean Theorem? Index Next >> Superstition Around Number 13
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Source of Plus and Multiplication Signals

The regular use of the + (plus) sign appears in John Widman d'Eger's Commercial Arithmetic, published in Leipzig in 1489. However, the plus and minus signs did not represent addition or subtraction, or positive or negative numbers, but excesses and deficits in business problems (Cajori vol.
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A strange prime number

The prime number 73939133 has a very strange property. If you remove the digits from the end, the numbers obtained are also prime. Note: 73939133 is a prime number 7393913 is a prime number 739391 is a prime number 73939 is a prime number 7393 is a prime number 739 is a prime number 7 is a prime number Origin of the relation signs (=, ) Index Next >> Origin of the word calculation
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Forming the Nine Times Table

First make a column from 0 to 9: 0 1 2 3 4 5 6 7 8 9 Then make a column from 9 to 0: 9 8 7 6 5 4 3 2 1 0 Now join the two together to get the results of the times tables of the nine: 09 18 27 36 45 54 63 72 81 90 * Submitted by Gabriel Pires Zampol What are the leap years? Index Next >> What is a pentagram?
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Origin of relation signs (=,)

Roberto Record, an English mathematician, will always have his name pointed out in the history of mathematics because he was the first to use the sign = (equal) to indicate equality. In his first book, published in 1540, Record placed the symbol between two equal expressions; the = sign, consisting of two small parallel dashes, only appeared in 1557.
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Count to one million

Did you know that if someone counted aloud to a million, 24 hours a day, without stopping - 1… 2… 3… - saying a digit or number per second, it would take no less than 12 days to finish the enumeration? The Russian Multiplication Method Table of Contents Next >> Who Discovered the Pythagorean Theorem?
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Gentle multiplication

Note this number: 21578943. Note that it has all significant digits except 6. Now multiply it by 6. 21578943 x 6 = 129473658 See that the result shows all significant digits, including 6. That is, multiplication, being kind, made it possible to entry of digit 6 in the previous number.
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Challenge 10

How many pages does the book have? Difficulty Level: If I read 5 pages a day of a book, I finish reading 16 days earlier than if I was reading 3 pages a day. How many pages does the book have? Challenge 9 Ducks and Dogs Challenge Index Next >> Challenge 11 Find the values ​​of x, y and z
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Old Fashioned Subtraction

In the year 830, Mohamed Ben Musa Alkarismí, one of the most notable sages of the 9th century, made subtractions of whole numbers as follows: was started from the left (operation I).
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Challenge 100

The King and the Slaves Difficulty Level: One king has bought five slaves. Two of them, who always told the truth, had brown eyes, and the other three (blue-eyed) always lied. The five were arranged in a row. The king should thus guess in what order they were willing, asking only three questions, one for each different slave.
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The magic number

1089 is known as the magic number. Here's why: Choose any number from three distinct digits: for example, 875. Now write this number backwards and subtract the smallest from the largest: 875 - 578 = 297 Now also invert this result and make the sum: 297 + 792 = 1089 (the magic number) Warning: Before you send us an email saying that it doesn't work with certain numbers, remember that three digits must be used in the calculation.
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What are nice numbers?

An integer n is sympathetic when there are positive integers a, b and c, such that: a 2 + b 2 - c 2. For example: 1 is a nice number, because 1 = 4 2 + 7 2 - 8 2. 3 is a nice number, because 3 = 4 2 + 6 2 - 7 2. The Origin of the Matrix Name Table of Contents Next >> Old-Fashioned Subtraction
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Who is your idol?

This is a prank you can email to your friends. Copy the text below, putting your name on item 9. When your friends do the math to find out their idols, the result will always be 9, meaning you will always be the chosen idol. If you want to know who you admire, do this little exercise: 1) Pick a number from 1 to 9 2) Multiply by 3 3) Add 3 4) Multiply again by 3 5) Add the two digits of the result Now look further down… vvvvvvvvv With the result of the calculation, look for your idol in the following list: 1.
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Challenge 123

Grandfather younger than father? Difficulty Level: I know someone whose grandfather is younger than his father. How is this possible? Challenge 122 How much should the jeweler pay? Challenge Index Next >> Challenge 124 The Death Sentence
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Challenge 124

The Death Sentence Difficulty Level: You are about to receive your death sentence. Assassins challenge him: - Make a statement. If what you say is a lie, you will die at the stake. If you speak the truth, you will be drowned. If we cannot define your statement as truth or lie, you will be set free.
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Challenge 121

Hosting Friends Difficulty Level: See below and try to find out the name of the place and the room number of the hotel where Fernando, Carlos and Joel were staying. People: Fernando, Carlos, Joel Places: Recife, Fortaleza, Porto Seguro Number of rooms in hotel: 305, 419, 538 1.
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Who invented trigonometry?

Trigonometry is not the work of one man or nation. Its history is thousands of years old and is part of every great civilization. From Hipparchus to modern times there was no trigonometric "reason." Instead, the Greeks and later the Hindus and Muslims used trigonometric lines.
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