Exactly Reaching

Part of the Triangles section of Coddy's Geometry journey. Lesson 8 of 63.

What if the two short sticks add up to exactly the long one? Sticks of 4, 6 and 10: 4 + 6 = 10. The short sticks do reach each other, but only when they lie flat along the long stick. The three "sides" are then one straight line, and there is no triangle at all.

So the inequality has to be strict: the two shorter sides must add up to more than the longest, not just as much. Equal gives a flat line; less gives sticks that never meet.

Challenge

AB is 8 long. Drag C until AC = 3 and BC = 5 at the same time, watching the readout. Where does C end up? Press Check when both lengths are right.

Try it yourself

$Drag the figure and watch$

Drag the figure and watch

Test yourself

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

All lessons in Triangles

2The Triangle Inequality

Can Three Sticks Meet?Exactly ReachingThe 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