Can Three Sticks Meet?

Part of the Triangles section of Coddy's Geometry journey. Lesson 1 of 60.

$A stick 7 long lying down, with sticks of 2 and 3 hanging from its ends, not touching$

Here sticks of 2 cm and 3 cm hang from the ends of a 7 cm stick. They can never meet. Together they are only $2+3 = 5$ cm long, and 5 is less than 7. In a triangle, any two sides added together must be longer than the third side.

Challenge

AB is a stick 8 long. Drag C so that AC = 5 and BC = 5. The three sticks then make a triangle. Press Check when you are done.

Try it yourself

$Drag the figure and watch$

Drag the figure and watch

All lessons in Triangles

1The Triangle Inequality

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

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 Test Recap: Right or Not

10Scale in the World

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

2Sides and Names

Sorting by Sides The Longest Side Ticks into Equations Recap: Sorting Triangles

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