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## Class 10 (Foundation)

### Unit 9: Lesson 4

Pythagoras theorem

# Pythagorean theorem example

Sal uses the Pythagorean theorem to find the height of a right triangle with a base of 9 and a hypotenuse of 14. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• Hey! At you say that if we know two of the sides we can use the pythagorean theorem, what can we do or what can we use if we only know one side?
• The Pythagorean theorem only works if you know two sides. If you only know one side and the triangle has been drawn accurately to scale, you might be able to get away with using a protractor and a ruler, but that again relies that you have the triangle actually drawn out and that it is to scale. I wouldn't advise it if accuracy is a concern unless you are actually instructed to do so.
• I was wondering can i just solve the problem like this??
a 2+9 2=14 2
so 14 -9 = 5
so can't it be 5 squared???( 5 2 )
• wow reading this... it says 11 years ago
• if we had a left 90o degree triangle, would the Pythagorean theorem work????
• The Pythagorean theorem ONLY works on 90 degree triangle aka right triangle.
• i really dont get y we need this like i am good without this in my life
• This is a fundamental part of architecture, buildings, etcetera. If you don't like this, then you'll never be able to buy a proper house and be easily scammed.
• How do you calculate a square root without a calculator ? Is it possible ?
• Daphne78, it is possible. For example, (-5)*(-5)=25, also 5*5=25. So √25 can either be (-5) or 5.
• Why didn’t he just go All the way to square root your supposed to have a decimal.
• You know about irrational numbers where the decimal goes on forever?

Which would you rather see? Sqrt(15) or 10.7238052948? Imaging performing operations on such a long decimal!

Decimals are not always preferred in maths (especially in algebra) for this reason. It's preferred that you leave it as a root or fraction to make the working easier.
• So is the Pythagorean theorem for other triangles too, or just for the right triangles?
• The Pythagorean theorem applies to right triangles only.

It is true that some problems involving non-right triangles can be solved using the Pythagorean theorem indirectly, but only by creating right triangles. For example, given the sides of an isosceles triangle, one can find the altitude to the unequal side by drawing this altitude, and then using the Pythagorean theorem on one of the two congruent right triangles formed by this altitude.

Have a blessed, wonderful day!
• But can you solve the question if i just give you the hypotenuse and another side to solve the third side?
• Yes. You can use the Pythagorean theorem to solve for a missing side.
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