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Sorting by the Test

Part of the Triangles section of Coddy's Geometry journey. Lesson 36 of 63.

With several triangles to sort, work through each the same way: find the longest side, square the other two and add, compare. Write the three results side by side and the sorting is done.

$Three triangles labelled 6, 8, 10 and 4, 8, 9 and 5, 7, 8$

6, 8, 10: 36 + 64 = 100, equal: right. 4, 8, 9: 16 + 64 = 80, less than 81: obtuse, only just. 5, 7, 8: 25 + 49 = 74, more than 64: acute. Small differences matter: 80 against 81 is still obtuse, so work it out rather than trusting the shape.

Challenge

Tap every right triangle among these three, then press Check.

Try it yourself

$Find the right part on the figure$

Find the right part on the figure

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Triangles

1Sides and Names

Three Sides, Three Corners Sorting by Sides Naming by Angles Ticks into Equations The Longest Side Recap: Sorting Triangles

4Area of a Triangle

Half the Rectangle Height Is Not a Side Right Triangle Area Finding the Height Any Side Can Be the Base Recap: Area

7Is It Right?

The Converse Testing a Triangle Acute or Obtuse?Sorting by the TestRecap: Right or Not

10Scale in the World

Shadows Across the River Nested Triangles A Side with an Expression Recap: Scale in the World

2The Triangle Inequality

Can Three Sticks Meet?Exactly Reaching The Range of the Third Side The Formula Recap: The Third Side

5The Pythagorean Theorem

Squares on the Sides Finding the Hypotenuse Pythagorean Triples When It Is Not Whole Recap: The Hypotenuse

8Special Right Triangles

The 45-45-90 Triangle Legs from the Hypotenuse The 30-60-90 Triangle All Three Sides Which Triangle Is It?Recap: Special Triangles

11Two Tools at Once

Height of an Isosceles Area from the Height The Equilateral Triangle Right Triangle Perimeter Recap: Two Tools