Parts of a Triangle Practice Problems - Sides, Perimeter & Types

Master triangle parts with interactive practice problems. Learn to identify sides, calculate perimeter, classify triangle types, and apply the triangle inequality theorem.

📚Master Triangle Parts with Step-by-Step Practice
  • Calculate triangle perimeter by adding all three sides together
  • Classify triangles as equilateral, isosceles, or scalene based on side lengths
  • Apply the triangle inequality theorem to determine valid triangle formations
  • Identify relationships between side lengths and opposite angles
  • Solve for unknown side lengths in equilateral triangles using perimeter
  • Determine if three given measurements can form a valid triangle

Understanding The sides or edges of a triangle

Complete explanation with examples

The sides of a triangle

Every triangle has three sides. That also works the other way around - if we see a shape with tree sides, it's a triangle.

types of triangles based on the sides:

The sides allow us to classify the different types of triangles according to their size:

  • Equilateral: All sides are equal, leading to equal angles.
  • Isosceles: Two sides are equal, with base angles also equal.
  • Scalene: All sides are different lengths, with all angles unique.
Perimeter of a Triangle

Like every polygon, the sides of a triangle form its perimeter. To find the perimeter of a triangle, simply add the lengths of all three sides.

A1 - Sides of a triangle
Relation between the sides and the angles in a triangle

In a triangle, there’s a direct relationship between the length of a side and the size of the angle across from it:
The Longer Side will always be in the opposite side of the larger Angle, and the shorter side will always be in the opposite side of the smaller Angle.

Can every three lines form a triangle?

In any triangle, the sum of the two shorter sides must always be greater than the length of the third side. This rule, known as the Triangle Inequality Theorem, ensures that the sides can actually form a closed triangle. For example, if the two shorter sides are not greater than the third, the sides would lie flat rather than forming a triangle. This principle is crucial in determining whether a set of side lengths can create a valid triangle.

Detailed explanation

Practice The sides or edges of a triangle

Test your knowledge with 36 quizzes

Which of the following is the height in triangle ABC?

AAABBBCCCDDD

Examples with solutions for The sides or edges of a triangle

Step-by-step solutions included
Exercise #1

Look at the triangle ABC below.

AD=12AB AD=\frac{1}{2}AB

BE=12EC BE=\frac{1}{2}EC

What is the median in the triangle?

AAABBBCCCEEEDDD

Step-by-Step Solution

A median in a triangle is a line segment connecting a vertex to the midpoint of the opposite side. Here, we need to find such a segment in triangle ABC \triangle ABC .

Let's analyze the given conditions:

  • AD=12AB AD = \frac{1}{2}AB : Point D D is the midpoint of AB AB .
  • BE=12EC BE = \frac{1}{2}EC : Point E E is the midpoint of EC EC .

Given that D D is the midpoint of AB AB , if we consider the line segment DC DC , it starts from vertex D D and ends at C C , passing through the midpoint of AB AB (which is D D ), fulfilling the condition for a median.

Therefore, the line segment DC DC is the median from vertex A A to side BC BC .

In summary, the correct answer is the segment DC DC .

Answer:

DC

Exercise #2

Look at triangle ABC below.

What is the median of the triangle and to which side is it drawn?

AAABBBCCCDDDEEE

Step-by-Step Solution

A median of a triangle is a line segment that connects a vertex to the midpoint of the opposite side. In triangle ABC \triangle ABC , we need to identify such a median from the diagram provided.

Step 1: Observe the diagram to identify the midpoint of each side.

Step 2: It is given that point E E is located on side AC AC . If E E is the midpoint of AC AC , then any line from a vertex to point E E would be a median.

Step 3: Check line segment BE BE . This line runs from vertex B B to point E E .

Step 4: Since E E is labeled as the midpoint of AC AC , line BE BE is the median of ABC \triangle ABC drawn to side AC AC .

Therefore, the median of the triangle is BE BE for AC AC .

Answer:

BE for AC

Exercise #3

Given the following triangle:

Write down the height of the triangle ABC.

AAABBBCCCEEEDDD

Step-by-Step Solution

An altitude in a triangle is the segment that connects the vertex and the opposite side, in such a way that the segment forms a 90-degree angle with the side.

If we look at the image it is clear that the above theorem is true for the line AE. AE not only connects the A vertex with the opposite side. It also crosses BC forming a 90-degree angle. Undoubtedly making AE the altitude.

Answer:

AE

Video Solution
Exercise #4

In an isosceles triangle, the angle between ? and ? is the "base angle".

Step-by-Step Solution

An isosceles triangle is one that has at least two sides of equal length. The angles opposite these two sides are known as the "base angles."
The side that is not equal to the other two is referred to as the "base" of the triangle. Thus, the "base angles" are the angles between each of the sides that are equal in length and the base.
Therefore, when we specify the angle in terms of its location or position, it is the angle between a "side" and the "base." This leads to the conclusion that the angle between the side and the base is the "base angle."

Therefore, the correct choice is Side, base.

Answer:

Side, base.

Exercise #5

Look at the two triangles below. Is EC a side of one of the triangles?

AAABBBCCCDDDEEEFFF

Step-by-Step Solution

Every triangle has 3 sides. First let's go over the triangle on the left side:

Its sides are: AB, BC, and CA.

This means that in this triangle, side EC does not exist.

Let's then look at the triangle on the right side:

Its sides are: ED, EF, and FD.

This means that in this triangle, side EC also does not exist.

Therefore, EC is not a side in either of the triangles.

Answer:

No

Video Solution

Frequently Asked Questions

How do you find the perimeter of a triangle?

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To find the perimeter of a triangle, simply add the lengths of all three sides together. For example, if a triangle has sides of 4 cm, 3 cm, and 5 cm, the perimeter is 4 + 3 + 5 = 12 cm.

What are the three types of triangles based on their sides?

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The three types are: 1) Equilateral - all three sides are equal, 2) Isosceles - two sides are equal, 3) Scalene - all three sides are different lengths. Each type also has corresponding angle properties.

What is the triangle inequality theorem?

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The triangle inequality theorem states that the sum of any two sides of a triangle must be greater than the length of the third side. This rule determines whether three given lengths can actually form a valid triangle.

How do you check if three sides can form a triangle?

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Check all three combinations: add the two shorter sides and verify the sum is greater than the longest side. For example, with sides 5, 7, and 10: check that 5+7>10, 7+10>5, and 5+10>7.

What is the relationship between triangle sides and angles?

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In any triangle, the longest side is always opposite the largest angle, and the shortest side is opposite the smallest angle. This direct relationship helps identify angle sizes based on side lengths.

How do you find the side length of an equilateral triangle from its perimeter?

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Since all three sides are equal in an equilateral triangle, divide the perimeter by 3. For example, if the perimeter is 21 cm, each side is 21 ÷ 3 = 7 cm.

Can a triangle have sides of 3 cm, 4 cm, and 8 cm?

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No, these sides cannot form a triangle. When you add the two shorter sides (3 + 4 = 7), the sum is less than the third side (8 cm), violating the triangle inequality theorem.

What are the parts of a triangle?

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A triangle has three main parts: three sides (edges), three vertices (corners), and three angles. The sides connect the vertices and form the perimeter, while angles are formed where two sides meet.

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