How to Use the Pythagorean Theorem to Find a Missing Leg in Right Triangles
FAQs on Pythagorean Theorem Find the Missing Leg Worksheet Practice
1. What is the Pythagorean Theorem?
The Pythagorean Theorem states that in a right triangle, a² + b² = c², where c is the hypotenuse. In this formula:
- a and b are the legs (shorter sides).
- c is the hypotenuse (longest side opposite the right angle).
2. How do you find the missing leg using the Pythagorean Theorem?
To find a missing leg, use the formula a = √(c² − b²) or b = √(c² − a²). Follow these steps:
- Step 1: Square the hypotenuse.
- Step 2: Subtract the square of the known leg.
- Step 3: Take the square root of the result.
3. What is the formula for finding a missing leg?
The formula for a missing leg in a right triangle is leg = √(hypotenuse² − other leg²). In symbols:
- a = √(c² − b²)
- b = √(c² − a²)
4. Can you give an example of finding a missing leg?
Yes, to find a missing leg, substitute known values into a² + b² = c² and solve. Example:
- Given: c = 13, b = 5
- Step 1: 13² = 169
- Step 2: 5² = 25
- Step 3: a² = 169 − 25 = 144
- Step 4: a = √144 = 12
5. How do you know which side is the hypotenuse?
The hypotenuse is the longest side of a right triangle and is always opposite the right angle. To identify it:
- Look for the 90° angle.
- The side directly across from that angle is the hypotenuse.
6. Can you use the Pythagorean Theorem on any triangle?
No, the Pythagorean Theorem only works for right triangles. A right triangle must have one 90° angle. If the triangle does not contain a right angle, this formula cannot be applied directly.
7. What are common mistakes when finding a missing leg?
Common mistakes when solving for a missing leg include subtracting incorrectly or mixing up the hypotenuse. Watch out for:
- Using a² + b² = c² incorrectly when solving for a leg.
- Forgetting to subtract instead of add.
- Not taking the square root at the final step.
- Choosing the wrong side as the hypotenuse.
8. Why do you subtract when finding a missing leg?
You subtract because you are rearranging a² + b² = c² to isolate one leg. If solving for a, then:
- a² = c² − b²
9. How do you check your answer when finding a missing leg?
To check your answer, substitute all three side lengths back into a² + b² = c². Example:
- If sides are 5, 12, and 13
- 5² + 12² = 25 + 144 = 169
- 13² = 169
10. Where is the Pythagorean Theorem used in real life?
The Pythagorean Theorem is used in construction, navigation, engineering, and distance calculations. Real-life applications include:
- Finding the length of a ladder against a wall.
- Calculating diagonal distances on maps.
- Determining shortest paths in coordinate geometry.





















