# Ch 4: Properties of Triangles: Help and Review

### About This Chapter

## Who's it for?

Anyone who needs help understanding high school geometry material will benefit from taking this course. You will be able to grasp the subject matter faster, retain critical knowledge longer and earn better grades. You're in the right place if you:

- Have fallen behind in understanding the different types of angles and the properties of triangles.
- Need an efficient way to learn about the properties of triangles.
- Learn best with engaging auditory and visual tools.
- Struggle with learning disabilities or learning differences, including autism and ADHD.
- Experience difficulty understanding your teachers.
- Missed class time and need to catch up.
- Can't access extra math learning resources at school.

## How it works:

- Start at the beginning, or identify the topics that you need help with.
- Watch and learn from fun videos, reviewing as needed.
- Refer to the video transcripts to reinforce your learning.
- Test your understanding of each lesson with short quizzes.
- Submit questions to one of our instructors for personalized support if you need extra help.
- Verify you're ready by completing the Properties of Triangles chapter exam.

## Why it works:

**Study Efficiently:**Skip what you know, review what you don't.**Retain What You Learn:**Engaging animations and real-life examples make topics easy to grasp.**Be Ready on Test Day:**Use the Properties of Triangles chapter exam to be prepared.**Get Extra Support:**Ask our subject-matter experts any relevant question. They're here to help!**Study With Flexibility:**Watch videos on any web-ready device.

## Students will review:

In this chapter, you'll learn the answers to questions including:

- What equations should I use to find the areas of rectangles and triangles?
- How can angles and sides help me classify triangles?
- What equations should I use to find the perimeters of rectangles and triangles?
- How do I define the exterior and interior angles of triangles?
- What steps should I follow to construct the median of a triangle?
- How do I determine the altitude, angle bisectors and median of a triangle?
- How do I construct different types of triangles?
- What terms should I use when working with the concurrent lines of a triangle?

### 1. Area of Triangles and Rectangles

How do you find out the area of rectangles and triangles? Learn how in this lesson! We'll look at the formulas, then practice solving problems for each shape.

### 2. Perimeter of Triangles and Rectangles

Without realizing it, we calculate and use the perimeter of triangles and rectangles in regular everyday situations. Learn more about the perimeter of triangles and rectangles in this lesson, and test your knowledge with a quiz.

### 3. How to Identify Similar Triangles

Similar triangles have the same characteristics as similar figures but can be identified much more easily. Learn the shortcuts for identifying similar triangles here and test your ability with a quiz.

### 4. Angles and Triangles: Practice Problems

Want more practice solving with angle pairs? How about more review for solving angles in triangles? Look no further. Get more practice here, and test your ability with a quiz.

### 5. Triangles: Definition and Properties

What makes a shape a triangle? In this lesson, we'll explore the definition of a triangle, then analyze the parts of triangles, including the vertices, base and height.

### 6. Classifying Triangles by Angles and Sides

Not all triangles are the same. There are equilateral, isosceles and scalene triangles. Then there are right, acute and obtuse triangles. In this lesson, we'll learn how to classify triangles using their sides and angles.

### 7. Interior and Exterior Angles of Triangles: Definition & Examples

Knowing just a few things about the interior or exterior angles of triangles is sometimes all you need to put all the pieces together. Find out more in this lesson.

### 8. Constructing the Median of a Triangle

If you have one triangle and want to divide it, you can use a median line. Medians have special geometric properties that we'll learn about in this lesson.

### 9. Median, Altitude, and Angle Bisectors of a Triangle

Line segments in triangles are just clutter; they have special names and qualities depending on how they're drawn. In this lesson, we'll learn about medians, altitudes and angle bisectors.

### 10. Constructing Triangles: Types of Geometric Construction

When you're asked to construct a triangle, it's time to break out that compass and straight edge! In this lesson, find out how to construct triangles no matter what you're given.

### 11. Properties of Concurrent Lines in a Triangle

Centroids, orthocenters, incenters, circumcenters, oh my! Don't worry though. In this lesson, we master the various terms for concurrent lines in triangles and match them to altitudes, angle bisectors, perpendicular bisectors and medians.

### 12. How to Find the Height of a Triangle

A triangle can be described using a variety of its characteristics, from its area, legs, hypotenuse, height, etc. This lesson will focus on the height of a triangle and two methods that can be used to solve when it is unknown.

### 13. Hypotenuse: Definition & Formula

The term hypotenuse refers to the longest side of a right triangle and has many properties important to both geometry and trigonometry. This lesson will describe the hypotenuse and give insight into its importance.

### 14. Included Angle of a Triangle: Definition & Overview

The included angle of a triangle can be found in many geometric theorems and can be very helpful when proving geometric concepts and solving problems. This lesson will define included angle and give some examples of how it can be used. There will be a quiz at the end of the lesson.

### 15. Inscribed Angle: Definition, Theorem & Formula

Circles are all around us in our world. Inscribed angles are angles that sit inside a circle with the vertex on the circumference of the circle. Inscribed angles have a special relationship with the intercepted arc.

### 16. Interior Angle Theorem: Definition & Formula

This lesson will define what an interior angle is, and it will provide and explain how to use the formula for finding the sum of the interior angles of a polygon. Examples will be provided detailing four of the ways it can be used.

### 17. Median of a Triangle: Definition & Formula

In this lesson, we will look at the definition and properties of a median of a triangle. We will also look at three different formulas to find the length of a median in a triangle.

### 18. Midsegment: Theorem & Formula

Learn about the midsegment of a triangle and the way in which it's found. Read about the properties of the midsegment as they relate to the base, angles, perimeter and area, and then test your knowledge with a short quiz.

### 19. Percent of Change: Definition, Formula & Examples

In this lesson, you'll learn what percent of change is and discover the formula to determine percent of change. You'll also see the formula in action in a few examples. Then, you can test your new knowledge with a brief quiz.

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### Other Chapters

Other chapters within the High School Geometry: Help and Review course

- Foundations of Geometry: Help and Review
- Logic in Mathematics: Help and Review
- Introduction to Geometric Figures: Help and Review
- Triangles, Theorems and Proofs: Help and Review
- Parallel Lines and Polygons: Help and Review
- Similar Polygons: Help and Review
- Quadrilaterals: Help and Review
- Circular Arcs and Circles: Help and Review
- Conic Sections: Help and Review
- Geometric Solids: Help and Review
- Analytical Geometry: Help and Review
- Introduction to Trigonometry: Help and Review