Triangle

Understanding Sides, Vertices, and Angles in Geometry

In geometry, shapes are defined by three key components: sides, vertices, and angles. These elements work together to form polygons and other figures, helping us understand their properties and relationships.

The number of sides in a polygon equals the number of vertices and angles. For example, a hexagon has six sides, six vertices, and six angles.

Definitions:

Side

A side is the straight line that lies between two points called vertices. An angle is formed between two lines. Sides form the edges of a polygon. For example, a triangle has three sides, while a square has four. The length and arrangement of sides determine the size and shape of a figure.

Vertex

A vertex is the point of origin where two or more straight lines meet, thus creating an angle. These vertices are often referred to as the "corners" of a shape. A triangle has three vertices, a square has four, and a pentagon has five.

Angle

An angle is created when two lines originate from the same vertex.  The measure of an angle indicates the degree of rotation between the two sides. Angles can be acute (less than 9090^\circ), right (9090^\circ), obtuse (greater than 9090^\circ), or straight (180180^\circ).

To clearly illustrate these concepts, we will represent them in the following drawing:

A1 - Side, Angle, Vertex

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Test yourself on angles!

einstein

In a right triangle, the sum of the two non-right angles is...?

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Exercises on Sides, Vertices, and Angles

Exercise 1

Assignment

Given the angles between parallel lines:

What is the value of: X X ?

Solution

We will mark the angle adjacent to the angle equal to 94o 94^o with the letter Z Z and find its value through the following calculation:

Z=18094=86 Z=180-94=86

Now we will focus on the triangle to find X X and remember that the sum of the angles in a triangle is equal to: 180o 180^o

X+86+53=180 X+86+53=180

X+139=180 X+139=180

X=180139 X=180-139

X=41 X=41

Answer

41o 41^o


Exercise 2

Assignment

At the vertices of a square with a side length of Y Y cm, 4 4 squares each with a side length of X X cm are drawn

What is the area of the entire shape?

Solution

The area of the entire shape is composed of the area of 4 4 small squares and the area of one large square.

Let's calculate the area of a small square

x×x=x2 x\times x=x^2

Therefore, the area of 4 4 squares will be equal to: 4x2 4x^2

The area of the large square is equal to: y×y=y2 y\times y=y^2

Thus, the total area of the shape will be equal to: 4x2+y2 4x^2+y^2

Answer

4x2+y2 4x^2+y^2


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Exercise 3

Prompt

Given that A,B A,B are two vertices in a rectangle.

How many rectangles can be drawn so that A,B A,B are adjacent vertices?

Solution

Answer:

4 4


Exercise 4

Assignment

Given that B,D B,D are two bisectors in a rectangle.

How many rectangles can be drawn so that BD BD is a diagonal in them?

Answer

3 3


Examples and Exercises with Solutions on Sides, Vertices, and Angles

Exercise #1

In a right triangle, the sum of the two non-right angles is...?

Video Solution

Step-by-Step Solution

In a right-angled triangle, there is one angle that equals 90 degrees, and the other two angles sum up to 180 degrees (sum of angles in a triangle)

Therefore, the sum of the two non-right angles is 90 degrees

90+90=180 90+90=180

Answer

90 degrees

Exercise #2

Calculate the size of angle X given that the triangle is equilateral.

XXXAAABBBCCC

Video Solution

Step-by-Step Solution

Remember that the sum of angles in a triangle is equal to 180.

In an equilateral triangle, all sides and all angles are equal to each other.

Therefore, we will calculate as follows:

x+x+x=180 x+x+x=180

3x=180 3x=180

We divide both sides by 3:

x=60 x=60

Answer

60

Exercise #3

Calculate the size of the unmarked angle:

160

Video Solution

Step-by-Step Solution

The unmarked angle is adjacent to an angle of 160 degrees.

Remember: the sum of adjacent angles is 180 degrees.

Therefore, the size of the unknown angle is:

180160=20 180-160=20

Answer

20

Exercise #4

a a is parallel to

b b

Determine which of the statements is correct.

αααβββγγγδδδaaabbb

Video Solution

Step-by-Step Solution

Let's review the definition of adjacent angles:

Adjacent angles are angles formed where there are two straight lines that intersect. These angles are formed at the point where the intersection occurs, one next to the other, and hence their name.

Now let's review the definition of collateral angles:

Two angles formed when two or more parallel lines are intersected by a third line. The collateral angles are on the same side of the intersecting line and even are at different heights in relation to the parallel line to which they are adjacent.

Therefore, answer C is correct for this definition.

Answer

β,γ \beta,\gamma Colateralesγ,δ \gamma,\delta Adjacent

Exercise #5

Lines a and b are parallel.

Which of the following angles are co-interior?

αααβββγγγδδδaaabbb

Video Solution

Step-by-Step Solution

Let's remember the definition of consecutive angles:

Consecutive angles are, in fact, a pair of angles that can be found on the same side of a straight line when this line crosses a pair of parallel straight lines.

These angles are on opposite levels with respect to the parallel line to which they belong.

The sum of a pair of angles on one side is one hundred eighty degrees.

Therefore, since line a is parallel to line b and according to the previous definition: the anglesβ+γ=180 \beta+\gamma=180

are consecutive.

Answer

β,γ \beta,\gamma

Do you know what the answer is?

How to Get Ready Quickly for a Surprise Exam?

The answer is quite simple.
Many students fear pop quizzes, but in reality, they are an opportunity to exercise and demonstrate your knowledge.
As long as you study throughout the year and not just before exams.

  • Knowing there will be a quiz usually motivates you to do your homework.
  • Avoid falling behind with the study material, and stay up-to-date with the latest classes.
  • Quizzes often test your knowledge on just one topic. For example: calculating the area of a trapezoid.
  • Quizzes are calculated into an annual average, so it's in your best interest to obtain the best possible grade on each one.

As long as you pay attention in class and do your homework, you have no reason to fear exams.


How to Realize We're Falling Behind with the Study Material?

Is there an area of geometry that you don't understand? That's normal, as there are topics you'll learn easily, and others that will be more challenging for you.

Important: don't fall behind with the study material, because in mathematics, the pace of learning is very fast.
The problem is that many topics are based on what was taught before. Therefore, the moment your understanding of a certain topic is partial, you will struggle to grasp the next topic.
How do you know if you've fallen behind with the study material?

  • You find it difficult to concentrate in class because you struggle to understand the teacher.
  • You have difficulty solving homework assignments.

You received a very low grade on a test, which reflects your level.

What can you do in this case?

  • You can ask a classmate to explain what you don't understand.
  • Ask your math teacher for help with the topic you haven't understood.
  • You can take lessons with a private tutor to explain the topic you haven't understood, from the beginning.

Study mathematics with a private tutor

There are students who struggle to keep up with the learning pace in class.
It's important to understand that the ability to quickly learn what is taught is not necessarily related to the student's ability to understand different topics taught, and even to pass exams with good grades.
Sometimes math teachers teach very quickly to cover all the topics of the annual program. This way, there are students who fail to properly understand the different explanations and formulas, and gradually fall behind.

With a private math tutor, you can not only learn all the topics you haven't understood, but also assimilate the material effectively.
A private tutor can help you pass high school exams, and of course, prepare you for college.
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This platform offers a wide variety of private tutors. You can read different opinions and comments about each teacher.
This means that you can quickly get an idea about the profile of each teacher, and thus you can easily choose the tutor who will accompany you in the learning process.


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