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For right triangles, the length of the hypotenuse squared equals the sum of the squares of the lengths of the legs.
The theorem can be used to find the length of the third side when two side lengths are known.
Notice that the side lengths of the outer square are equal to (a+b). Additionally, the side lengths of the inner square are equal to c. The area of both squares and the area of the four triangles are as follows.
| Area of the Inner Square | Area of the Outer Square | Area of the Four Triangles |
|---|---|---|
| c^2 | (a+b)^2 | 4* ab/2 = 2ab |
The area of the outer square equals the sum of the area of the inner square and the area of the four triangles. The previous diagram shows that. (a+b)^2=c^2+2ab This equation can be simplified by expanding the square of the binomial on the left-hand side.
a^2=a* a
Distribute (a+b)
Distribute a & b
Add terms
LHS-2ab=RHS-2ab
Next, apply the Geometric Mean Leg Theorem. Doing this relates the lengths of the legs to the length of the hypotenuse. a^2 = x* c b^2 = y* c These two equations can be added. Then, c can be factored out from the right-hand side. a^2 &= x* c [-0.15cm] ^+ b^2 &= y* c [-0.5ex] [-3ex] a^2+b^2 &= x* c+ y* c a^2+b^2 &=( x+ y)c Drawing the altitude resulted in the outcome that x+ y is equal to c. After substituting this into the equation above and simplifying, the Pythagorean Theorem is obtained. a^2+b^2 &= c* c &⇕ a^2+b^2 &= c^2