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

DB is a side in triangle ABC

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Examples with solutions for The sides or edges of a triangle

Step-by-step solutions included
Exercise #1

Can a triangle have a right angle?

Step-by-Step Solution

To determine if a triangle can have a right angle, consider the following explanation:

  • Definition of a Right Angle: An angle is classified as a right angle if it measures exactly 9090^\circ.
  • Definition of a Right Triangle: A right triangle is a type of triangle that contains exactly one right angle.
  • According to the definition, a right triangle specifically includes a right angle. This is a well-established classification of triangles in geometry.

Thus, a triangle can indeed have a right angle and is referred to as a right triangle.

Therefore, the solution to the problem is Yes.

Answer:

Yes

Video Solution
Exercise #2

Is the straight line in the figure the height of the triangle?

Step-by-Step Solution

The triangle's altitude is a line drawn from a vertex perpendicular to the opposite side. The vertical line in the diagram extends from the triangle's top vertex straight down to its base. By definition of altitude, this line is the height if it forms a right angle with the base.

To solve this problem, we'll verify that the line in question satisfies the altitude condition:

  • Step 1: Identify the triangle's vertices and base. From the diagram, the base appears horizontal, and the vertex lies directly above it.
  • Step 2: Check the nature of the line. The line is vertical when the base is horizontal, indicating perpendicularity.
  • Conclusion: The vertical line forms right angles with the base, thus acting as the altitude or height.

Therefore, the straight line depicted is indeed the height of the triangle. The answer is Yes.

Answer:

Yes

Video Solution
Exercise #3

Is the straight line in the figure the height of the triangle?

Step-by-Step Solution

To determine if the straight line is the height of the triangle, we'll analyze its role within the triangle:

  • Step 1: Observe the triangle and the given line. The triangle seems to be made of three sides and a vertical line within it.
  • Step 2: Recall that the height of a triangle, in geometry, is defined as a perpendicular dropped from a vertex to the opposite side.
  • Step 3: Examine the positioning of the line: The vertical line starts at one vertex of the triangle and intersects the base, appearing to be perpendicular.
  • Step 4: Verify perpendicularity: Given that the line is shown as a clear vertical (and a small perpendicular indicator suggests perpendicularity), we accept this line as the height.
  • Step 5: Conclude with verification that the line is effectively meeting the definition of height for the triangle in the diagram.

Therefore, the vertical line in the figure is indeed the height of the triangle.

Yes

Answer:

Yes

Video Solution
Exercise #4

Can a plane angle be found in a triangle?

Step-by-Step Solution

To determine whether a plane angle can be found in a triangle, we need to understand what a plane angle is and compare it to the angles within a triangle.

  • A plane angle is an angle formed by two lines lying in the same plane.
  • In the context of geometry, angles found within a triangle are the interior angles, which are the angles between the sides of the triangle.
  • Although the angles in a triangle are indeed contained within a plane (since a triangle itself is a planar figure), when referencing "plane angles" in geometry, we usually consider angles related to different geometric configurations beyond those specifically internal to defined planar shapes like a triangle.
  • The term "plane angle" typically refers to the measurement of an angle in radians or degrees within a plane, but this doesn't specifically pertain to angles of a triangle.

Therefore, based on the context and usual geometric conventions, the concept of a "plane angle" is not typically used to describe the angles found within a triangle. Thus, a plane angle as defined generally in geometry is not found specifically within a triangle.

Therefore, the correct answer to the question is No \text{No} .

Answer:

No

Video Solution
Exercise #5

Is the straight line in the figure the height of the triangle?

Step-by-Step Solution

In the given problem, we have a triangle depicted with a specific line drawn inside it. The question asks if this line represents the height of the triangle. To resolve this question, we need to discern whether the line is perpendicular to one of the sides of the triangle when extended, as only a line that is perpendicular from a vertex to its opposite side can be considered the height.

The line in question is shown intersecting one of the sides within the triangle but does not form a perpendicular angle with any side shown or the ground (as is required for it to be the height of the triangle). A proper height would typically intersect perpendicularly either at or along the extended line of the opposite side from a vertex.

Therefore, based on the visual clues provided and the typical geometric definition of a height (or altitude) in a triangle, this specific line does not fit the criteria for being a height.

Thus, we conclude that the line depicted is not the height of the triangle. The correct answer is No.

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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