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Pythagoras's Theorem

In any right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.

i.e.: c^2 = a^2 + b^2 in the following diagram:



(Diagram of a triangle needed)



Example

Find AC in the diagram below.

AB^2 + AC^2 = BC^2

AC^2 = BC^2 - AB^2

= 13^2 - 5^2

= 169 - 25 = 144

AC  = 12\mathsf{cm}.


(diagram missing)


Pythagorean Triangles

There are two common triangles that you must know.


The 3-4-5 triangle

3^2 + 4^2 = 5^2

9+16=25


and the 5-12-13 triangle

5^2 + 12^2 = 13^2

25+144=169


Image:Triangle_Pythagoras.gif


Comments

This is a basic Pythag article. A more basic first example is needed (where you find the hypotenuse). Looking at contextual questions is needed, as most exam questions would be of that sort.

Either extend this article or create a new one looking at pythag in 3D. Also, the connections with shapes, angle properties and trigonometry need to be explored for 'solving' triangles, checking congruency and basic solving of more 'difficult' real life problems.

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