The Pythagorean Theorem
Aligned to 8.G.B.7 — Common Core State Standards for Mathematics.
What this lesson teaches
In a right triangle, the squares of the two legs add up to the square of the hypotenuse: a² + b² = c². Use it to find a missing side.
Worked example
Legs 3 and 4: c² = 3² + 4² = 9 + 16 = 25, so c = √25 = 5.
Practice questions
- Find the hypotenuse with legs 6 and 8.
- A ladder reaches 12 ft up a wall with its base 5 ft out. How long is it?
- If c = 13 and one leg is 5, find the other leg.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
El Teorema de Pitágoras
En un triángulo rectángulo, la suma de los cuadrados de los dos catetos es igual al cuadrado de la hipotenusa: a² + b² = c². Úsalo para encontrar el lado que falta.
Ejemplo: Catetos 3 y 4: c² = 3² + 4² = 9 + 16 = 25, entonces c = √25 = 5.
More Geometry lessons
Properties of Transformations8.G.A.1Congruence Through Transformations8.G.A.2Transformations on the Coordinate Plane8.G.A.3Similarity Through Dilations8.G.A.4Angle Relationships8.G.A.5The Pythagorean Theorem8.G.B.6
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