How to Find the Unknown Length of a Triangle
If you know the length of two sides of a triangle, how to determine the length of the third side is a well known math fact. The equation is generally attributed to Pythagoras, who lived during the 5th and 6th centuries, B.C. Whether Pythagoras originated the equation now known as the Pythagorean Theorem is open to some debate, but we do know people have known how to do it for at least 2,500 years.
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Instructions
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1
Know that the formula for determining the length of the side of a triangle is A squared plus B squared equals C squared.
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2
Take the length of one known side of the triangle. Multiply that number by itself. For example, if the length of side a of the triangle is 2 inches, your result would be 4 inches (2 x 2 = 4).
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3
Take the length of the other known side of the triangle. Multiply that number by itself. For example, if the length of side B of the triangle is 3 inches, your result would be 9 inches (3 x 3 = 9).
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4
Add the result of Step 2 to the result of Step 3. In the example, the sum would be 13 inches (4 + 9 = 13).
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5
Determine the length of the final, unknown, side of the triangle by taking the square root of the result of Step 4. In our example, the length of the unknown side is 3.6 inches (√13 = 3.6).
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Tips & Warnings
A square root is the number that you multiply by itself to get another number. For example, the square root of 4 is 2. The square root of 25 is 5.
References
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Comments
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I'm learning :D
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Pealer At Work
Jan 06, 2011
that answer is incorrect. if A=2 B=3 C cannot = 3.6 because inversely, 3.6 squared plus 3 squared = 22,.. and the square root of 22 = 4.6.. changing Side A's value. Pythagorean only works for the hypotenuse of a right triangle... AND ONLY the hypotenuse. you would need trig and at least one angle if all you have is 2 sides and it is NOT a right triangle.
