The perimeter of a triangle is the sum of all three sides. So with the height (side "a") and base (side "b") known, you will need to determine the length of the third side, the hypotenuse (side "c"). This is a common problem you will be asked to answer when working with right triangles, those with a 90-degree angle. If it is a right triangle, then you can solve for side "c" by using the Pythagorean theorem: a^2 + b^2 = c^2. The carrot sign "^" indicates that the variables are raised to a certain power; in this case they are all being squared.
Instructions
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1
Plug the height and base into the Pythagorean theorem as variables "a" and "b." In this example, height equals 3 and base equals 4. This gives you 3^2 + 4^2 = c^2.
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2
Square the height and base and then calculate their sum: 9 + 16 = c^2
simplifies to 25 = c^2.
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3
Solve for "c" by taking the square root of both sides. This gives you the length of the third side: c = 5.
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4
Add the values of all three sides together to find the triangle's perimeter: 3 + 4 + 5 = 12.