High School Geometry: Free Course

About this course

Geometry connects measurement with proof. This high-school course brings together transformations, congruence, similarity, coordinate methods, circles, trigonometry and three-dimensional measurement. Study the complete public source playlist from Khan Academy in English, with all 205 recordings in the on-site classroom. Original lesson titles, source order and repeated entries are preserved.

Course at a glance

What you’ll learn

• Use transformations to analyze congruence and similarity.
• Construct and justify triangle, quadrilateral and circle relationships.
• Apply coordinates and trigonometry to geometric problems.
• Calculate areas, surface areas and volumes with stated assumptions.

Skills you’ll gain

• Geometric proof
• Transformations
• Circle theorems
• Spatial measurement

Course Overview

The broad source curriculum contains construction demonstrations, theorem proofs and applied problems. Rigid transformations explain congruence, while dilations and proportional reasoning support similarity. Coordinate examples connect slopes, distances and midpoints with geometric claims. Triangle and circle theorems lead into right-triangle trigonometry, the laws of sines and cosines, arcs and sectors. Nets, cross sections, surface area and volume extend the reasoning to solids. The original playlist order interleaves these topics, so the searchable lesson list is useful for revisiting a particular strand. A drawing provides a representation; a proof must identify the given facts and justify each conclusion without relying only on appearance.

How to study the course

• Videos 1–51: this part of the source list includes “Constructing square inscribed in circle” through “Basic trigonometry II”. Label what is given before applying a property. Keep a brief working note, revisit an unclear explanation and test one example before moving to another part of the material.
• Videos 52–102: this part of the source list includes “Proof: Rhombus diagonals are perpendicular bisectors” through “Parallel and perpendicular lines intro”. Separate an observation in a drawing from a justified conclusion. Keep a brief working note, revisit an unclear explanation and test one example before moving to another part of the material.
• Videos 103–153: this part of the source list includes “Law of sines” through “Basic geometry: language and labels”. Redraw an example with different dimensions or orientation. Keep a brief working note, revisit an unclear explanation and test one example before moving to another part of the material.
• Videos 154–205: this part of the source list includes “Quadrilaterals: kites as a geometric shape” through “Volume density”. Explain the relationship that supports the answer. Keep a brief working note, revisit an unclear explanation and test one example before moving to another part of the material.

Who is this for?

This course suits learners studying geometry and teachers looking for recorded explanations of the named geometric topic. It also provides a recorded reference for revisiting a topic after an earlier lesson or study attempt. Choose examples appropriate to your background and allow time to work through the method instead of judging understanding only by how familiar the terminology sounds.

Before you start

Basic arithmetic and the algebra used in the examples are useful. Keep paper, a ruler and a compass when constructions are demonstrated.

Put the lessons into practice

Create a small geometry portfolio: one compass-and-straightedge construction, one coordinate proof and one volume problem. Label the givens and explain each inference. Compare a diagram-based estimate with the calculated result. Include an example where two figures look alike but the available information does not establish congruence or similarity.

This optional study activity is provided by WikiFree for independent practice. Keep your working notes and use the relevant classroom recording to check a step, definition or interpretation. It is not an instructor-marked assignment.

Certificate / Assessment

Watching the public videos and using WikiFree completion tracking does not award a certificate, academic credit, an examination voucher or instructor assessment. Use your practice output to review what you can explain and repeat independently. The recorded lessons provide study material; completion tracking records your progress through that material.

Frequently asked questions

Provider: Khan Academy. Videos play from the Khan Academy channel on YouTube.