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### Course: Algebra basics>Unit 8

Lesson 3: Pythagorean theorem

# Intro to the Pythagorean theorem 2

Sal introduces the famous and super important Pythagorean theorem!  Created by Sal Khan and CK-12 Foundation.

## Want to join the conversation?

• If I have 16+64="c"2 or squared how do I square root it? I mean square root 80.
• You don't even have to simplify the square root of 80. Just right it as √80 and you are done! This is because 80 doesn't have a perfect square root. It has a decimal, with an infinite amount of numbers after it.
• What are some practical uses for the Pythagorean Theorem?
I am curious because I find it very interesting and I want to know how I can use it.
• How long of a ladder do you need to climb a 10 foot wall when you have to place the base of the ladder 5 feet from the wall? Square Root(10^2 + 5^2)...
• try the course on squares, square roots, and radicals
• I'm so confused with the pratice problems. I'm usually really good in this topic, but since when do you put the AB and AC stuff together? I Don't know if I'm making any sense though.
• I think I get whet you're saying. . The theorem says A squared plus B squared equals C squared, so if you find a and b you can find C. The same goes for finding AC, AB, BC, or any other combo. if you find the other two, you can find the answer by turning i tinto an equation.
• how can I use pythagorean Theorem in my daily life. I am curious to know about it
• Pythagorean theorem is used in every case of our life....if u know the base and height of a tower....u can know the distance between that and u.....u can also find out distance between points in co-ordinate geometry.....
• for the third (final) practice problem, at the minute marker, b = the square root of 24^2 - 12^2. Since both terms under the square root are raised to the same power, I tried to subtract 24^2 from 12^2 and end up with b = 12. This is different than the final answer, and was just curious as to why this doesn't work...
• One of the fundamental rules in mathematics is to be sure and follow "the order of operations". This order is frequently referred to as PEMDAS (which is a pneumonic)
1. Parenthesis (or any grouping symbols such as brackets or braces) do what is inside the parenthesis first.
2. Exponents
3. Multiplication and Division, do in order from left to right
4. Addition and Subtraction, do in order from left to right
• In terms of "acceptable formats" for problem solving of Pythagorean Theorem is it possible to allow answers rounded off to two decimal places? This would allow the students the opportunity to practice with their calculators too.
• At , Sal says in the 2nd right triangle a=28 which is bigger than 21 but the 21 side is bigger?
• Sachin,
The drawing was 'not to scale'.
Even though he said it was a triangle that "looks like this", when he drew it, he only knew the hypotunuse and he knew one side, but he did not know until he did the calculation whether the "a" side was larger or smaller than 21.

So he just drew any right triangle and labeled the sides with the known information.
As it turned out, the triangle he drew did not truly represent the angles and lengths of a right triangle that has a hypotunuse of 35 and one length of 21.

I hope that helps.
• What are Pythagorean triples?
• ""Pythagorean triples" are integer solutions to the Pythagorean Theorem, a2 + b2 = c2. I like "triplets," but "triples" seems to be the favored term. For a right triangle, the c side is the hypotenuse, the side opposite the right angle."
Example:
3^2 + 4^2 = 5^2