# Geometry

Contents

Finally, we're getting to geometry. We've been waiting for this and hope you have been, too. The foundation of all geometry is the line--so that's a great place to start. From there we'll move into angles, quadrilaterals, and triangles. Our goal here is to get familiar with the basic concepts, skills, and applications of geometry. So jump in and let's go for a ride!

## Lines, line segments, and rays

Let's draw points, lines, line segments, and rays. We'll also think about perpendicular and parallel lines and identify these in two-dimensional figures. Common Core Standard: 4.G.A.1

Terms & labels in geometry

Sal discusses geometry terms like point, line, and ray. He also shows to label them.

Lines, line segments, & rays

Sal discusses the difference between lines, line segments, and rays.

Identify rays, lines, & line segments

Recognize rays, lines, and line segments in geometric figures.

Draw rays, lines, & line segments

Draw rays, lines, and line segments with given points.

## Parallel and perpendicular

Learn the definitions of "parallel" and "perpendicular".

Intro to parallel & perpendicular lines

Sal discusses how to tell if lines are parallel or perpendicular.

Parallel & perpendicular lines

Sal identifies parallel and perpendicular lines in geometric figures.

Identify parallel and perpendicular lines

Recognize parallel and perpendicular lines in geometric figures and pictures.

Drawing parallel line segments

Sal draws parallel line segments with given points.

Draw parallel and perpendicular lines

Practice drawing parallel and perpendicular lines, line segments, and ray.

## Angle introduction

What is an angle and how do we label, measure and construct them? Great question. Luckily we have all your answers! To begin our journey towards understanding angles, we'll learn terms like vertex, acute, obtuse, circle arc, circumference, and protractor. These basic angle concepts will get you on the road to angle domination!

Intro to angles

Sal introduces angles and parts of an angle, like the vertex.

Naming angles

Sal names angles based on their vertex and endpoints.

Name angles

Name angles by their vertex, endpoints, or labels.

## Measuring angles

Learn how to measure angles using a protractor.

Measuring angles in degrees

Sal measures an angle with a protractor.

Measuring angles using a protractor 2

Sal measures several angles with a protractor.

Measuring angles using a protractor

Sal uses a virtual protractor to measure some angles.

Measure angles

Measure angles using a protractor.

## Constructing angles

Learn how to draw angles using a protractor.

Constructing angles

Sal uses a protractor to create 10° and 155° angles.

Draw angles

Use a protractor to construct angles.

## Angles in circles

Learn how to measure angles using a circle protractor and solve word problems about angles as part of a circle.

Angle measurement & circle arcs

Sal measures angles as part of a circle.

Angles in circles

Practice measuring angles using a circle protractor, solve word problems about angles as part of a circle.

## Angle types

Now that we know what angles are, let's dig a bit deeper and classify them and understand their properties better. Acute, obtuse, right, adjacent--all are angles that we will be become familiar with.

Acute, right, & obtuse angles

Sal discusses acute, obtuse, and right angles and shows examples of each.

Measuring angles in degrees

Sal measures an angle with a protractor.

Angle types

Determine if an angle is acute, right, or obtuse. A protractor is provided.

Recognizing angles

Sal identifies acute, obtuse, and right angles in diagrams and pictures.

Recognize angles

Determine if angles in shapes and pictures are acute, right, or obtuse.

Drawing acute, right and obtuse angles

Sal draws acute, right, and obtuse angles with given points.

Draw right, acute, and obtuse angles

Create an acute, right, or obtuse angle using a given vertex.

Identifying an angle

Sal matches pictures of angles to their degrees.

Benchmark angles

Estimate the size of angles when given a picture or a situation.

## Decomposing angles

Decomposing an angle

Sal finds the measure of angles by adding or subtracting.

Decompose angles

Find an angle's measure when given the measures of its parts.

## Line of symmetry

A line of symmetry for a two-dimensional figure is a line across the figure such that the figure can be folded along the line into matching parts. In this tutorial, we'll identify line-symmetric figures and draw lines of symmetry. Common Core Standard: 4.G.A.3

Intro to reflective symmetry

Sal introduces the concept of an "axis of symmetry."

Identify lines of symmetry and symmetrical figures

Draw and identify lines of symmetry. Create and identify symmetrical shapes.

Draw lines of symmetry and symmetrical figures

Practice drawing lines of symmetry and creating symmetrical figures.

## Classifying triangles

Triangles can be classified in different ways. In this tutorial, we'll learn about scalene, isosceles, equilateral, acute, right, and obtuse triangles.

Classifying triangles 1

Sal categorizes triangles as scalene, isosceles, equilateral, acute, right, or obtuse.

Classifying triangles by angles

You say you can't categorize a triangle because you don't know the length of the sides. Guess what? If you know the size of the angles you can!

Classifying triangles 2

Sal categorizes triangles as scalene, isosceles, equilateral, acute, right, or obtuse.

Identify triangles by angles

Practice identifying triangles by their angles as acute, right, or obtuse.

Identify triangles by side lengths

Practice identifying triangles by their side-lengths as equilateral, isosceles, or scalene.

## Classifying geometric shapes

Some practice classifying geometric shapes.

Classifying shapes by line and angles types

Sal categorizes shapes based on their sides and angles.

Quadrilateral properties

Sal discusses the properties of quadrilaterals, parallelograms, trapezoids, rhombuses, rectangles, and squares.

Classify shapes by line and angle types

Classify shapes based on pictures or attributes, such as angle types and side-lengths.