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Greetings from Brasil....

From Pythagoras we have

AB² = AC² + BC²

13² = 12² + X²

X = 5

Ver imagen tomson1975

Answer:

5 cm

Step-by-step explanation:

Pythagoras theorem gives us:

[tex]hypotenuse^{2} = side^{2} + side^{2}[/tex]

We know the hypotenuse is 13 cm.

We know one side is 12 cm.

[tex]13^{2} = 12^{2} + side^{2}[/tex]

[tex]169= 144 + side^{2}[/tex]

Subtracting 144 from both sides:

[tex]25 = side^{2}[/tex]

Reversing the sides:

[tex]side^{2}=25[/tex]

[tex]\sqrt{side^{2}}= \±\sqrt{25}[/tex]

[tex]side = \±\sqrt{25}[/tex]

[tex]side = \±5[/tex]

Since a distance can't be negative:

[tex]side=5[/tex]

The third side is 5 cm.