Isosceles Triangle Properties: Identifying the Name of the Third Side

Triangle Properties with Side Classification

In an isosceles triangle, the third side is called?

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Step-by-step written solution

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1

Understand the problem

In an isosceles triangle, the third side is called?

2

Step-by-step solution

To solve this problem, we need to understand what an isosceles triangle is and how its sides are labeled:

  • In an isosceles triangle, there are two sides that have equal lengths. These are typically called the "legs" of the triangle.
  • The third side, which is not necessarily of equal length to the other two sides, is known as the "base."

In terms of the problem, we want to determine the term used for the third side, which is the side that is not one of the two equal sides.

The correct term for the third side in an isosceles triangle is the "base." This is because the third side serves as a different function compared to the equal sides, which usually form the symmetrical parts of the triangle.

Among the given answer choices, choosing "Base" correctly identifies the third side of an isosceles triangle.

Therefore, the third side in an isosceles triangle is called the base.

Final Solution: Base

3

Final Answer

Base

Key Points to Remember

Essential concepts to master this topic
  • Definition: Isosceles triangles have two equal sides called legs
  • Terminology: The third unequal side is always called the base
  • Verification: Check that two sides are equal and identify the different one ✓

Common Mistakes

Avoid these frequent errors
  • Confusing leg and base terminology
    Don't call the equal sides the 'base' or the unequal side a 'leg' = wrong triangle vocabulary! This confuses the fundamental structure of isosceles triangles. Always remember that the base is the different side, while legs are the two equal sides.

Practice Quiz

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Is DE side in one of the triangles?
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FAQ

Everything you need to know about this question

Why is the third side specifically called the 'base'?

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The base gets its name because it often sits at the bottom of the triangle when drawn. More importantly, it's the side that's different from the two equal sides (legs), making it the foundation that distinguishes an isosceles triangle.

What if all three sides are equal?

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If all three sides are equal, you have an equilateral triangle, not just isosceles! In this special case, any side can be called the base, but we usually still pick one to work with.

Do the legs always have to be longer than the base?

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No! The legs can be shorter, longer, or even theoretically equal to the base. The key is that the two legs are equal to each other, regardless of their relationship to the base length.

How can I remember which side is the base?

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Think of it as the odd one out! In an isosceles triangle, two sides match (the legs) and one doesn't (the base). The base is always the different one.

What if I can't tell which sides are equal?

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Look for equal marks on the diagram, or check the given measurements. The two sides with identical lengths or markings are the legs, and the remaining side is automatically the base.

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