Learn the basics of geometryâ€”the core skills you'll need for high school and college math. From Khan Academy

### Lines - Basic Geometry

Learn what lines, line segments, and rays are and how to use them.

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### Angles - Basic Geometry

In this topic, we will learn what an angle is and how to label, measure and construct them. We will also explore special types of angles.

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Measuring angles with a circular protractor

# Measuring angles with a circular protractor

### Shapes - Basic Geometry

Classify shapes and solve problems using what we know of the properties of shapes.

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Cousin Fal's Shape Collection (Identifying Shapes)

# Cousin Fal's Shape Collection (Identifying Shapes)

Classifying shapes by line and angles types

# Classifying shapes by line and angles types

Quadrilaterals: Kites as a geometric shape

# Quadrilaterals: Kites as a geometric shape

### Coordinate Plane - Basic ...

We use coordinates to describe where something is. In geometry, coordinates say where points are on a grid we call the "coordinate plane". From Khan Academy Basic Geometry

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Drawing a quadrilateral on the coordinate plane ex...

# Drawing a quadrilateral on the coordinate plane example

Coordinate plane graphing word problem - Naomi wa...

# Coordinate plane graphing word problem - Naomi walks to school

Area of a parallelogram on the Coordinate Plane

# Area of a parallelogram on the Coordinate Plane

Dimensions of a rectangle from coordinates

# Dimensions of a rectangle from coordinates

### Area and Perimeter - Basi...

Area and perimeter help us measure the size of 2D shapes. Weâ€™ll start with the area and perimeter of rectangles. From there, weâ€™ll tackle trickier shapes, such as triangles and circles. From Khan Academy Basic Geometry.

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Measuring rectangles with different unit squares

# Measuring rectangles with different unit squares

Counting unit squares to find area formula

# Counting unit squares to find area formula

Circles: Radius, diameter, circumference, and Pi

# Circles: Radius, diameter, circumference, and Pi

Finding circumference of a circle when given the a...

# Finding circumference of a circle when given the area

Transitioning from unit squares to area formula

# Transitioning from unit squares to area formula

Finding perimeter when a side length is missing

# Finding perimeter when a side length is missing

Finding missing side length when given perimeter

# Finding missing side length when given perimeter

### Volume and Surface Area -...

Volume and surface area help us measure the size of 3D objects. Weâ€™ll start with the volume and surface area of rectangular prisms. From there, weâ€™ll tackle trickier objects, such as cones and spheres. From Khan Academy Basic Geometry.

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Volume of a rectangular prism: fractional dimensio...

# Volume of a rectangular prism: fractional dimensions

Volume of a rectangular prism: word problem

# Volume of a rectangular prism: word problem

Surface area using a net: rectangular prism

# Surface area using a net: rectangular prism

Surface area using a net: triangular prism

# Surface area using a net: triangular prism

How volume changes from changing dimensions

# How volume changes from changing dimensions

### Pythagorean theorem - Bas...

The Pythagorean theorem describes a special relationship between the sides of a right triangle. Even the ancients knew of this relationship. In this topic, weâ€™ll figure out how to use the Pythagorean theorem and prove why it works. From Khan Academy Basic Geometry.

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Pythagorean theorem word problem: fishing boat

# Pythagorean theorem word problem: fishing boat

Garfield's proof of the Pythagorean theorem

# Garfield's proof of the Pythagorean theorem

Bhaskara's proof of the Pythagorean theorem

# Bhaskara's proof of the Pythagorean theorem

Pythagorean theorem proof using similarity

# Pythagorean theorem proof using similarity

Use Pythagorean theorem to find area of an isoscel...

# Use Pythagorean theorem to find area of an isosceles triangle

### Transformations, congruen...

Learn about geometric transformations and how they're used to understand the meaning of "similar" and "congruent". From Khan Academy Basic Geometry.

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