The formula can be changed around to find the length of an unknown side when the other two sides are known.

**The formula is used to find**

the length of the hypotenuse when the

lengths of the two legs are known.

In this example, we know the length of the legs

**a** and **b,** but not the length of the hypotenuse, **c.**

To find the length of the hypotenuse,

- Replace the variables of the formula with the lengths of the legs.
- Do the calculations. The answer is the length of the hypotenuse
**c.**

Here is this formula worked on the calculator.

Remember: the keys and react to whatever is on the display when they are pushed.

10' is the length of the hypotenuse.

**Hypotenuse length practice:** Find the length of the hypotenuse using the two sides given. Convert the numbers with units of measurement to include fractions. Round off the rest of the numbers to 4 decimal places. **Remember: **

If you have difficulty squaring mixed numbers, refresh your memory here.

a b a b
(1) 6 9 (7) 9'4 3/4" 12'11"
(2) 5 10 (8) 1.73" 2.32"
(3) 22" 33" (9) 104'3" 77'7"
(4) 2.5" 7.5" (10) 19 25
(5) 10 3/8" 7 7/16" (11) 16 15/16" 22 15/16"
(6) 7'8" 3'6" (12) 24 24

**Answers.**