Learn Trigonometry
Right triangles, the unit circle, trig graphs, identities, equations and the laws of sines and cosines. You do every step, and the board checks each one.
287 lessons286 challenges690 quiz questions
- Beginner friendly
Hands-on interactive lessons
Audio narration on every lesson
Quizzes to test your knowledge
Free certificate of completion
Syllabus
Section 1
Right-Triangle Trigonometry
Start sectionStartFind any side or angle of a right triangle from the parts you know: name the sides, pick sine, cosine or tangent, solve and round, or give the exact value at 30°, 45° and 60°. Then use it on heights, distances, ramps and ladders, with angles of elevation and depression.Measuring With an Angle
3 lessons3The Three Ratios
4 lessons4Finding a Side
6 lessons610Finding the Hypotenuse
5 lessons510Finding an Angle
6 lessons65Special Triangles, Exactly
5 lessons55Elevation and Depression
6 lessons610Reciprocal Ratios
5 lessons510Final Challenges
6 lessons630Section 2
Angles and the Unit Circle
Start sectionStartPlace any angle in degrees or radians, convert between the two, and find arc lengths and sector areas. Read exact sine, cosine and tangent values at every special angle from the unit circle, using the reference angle and the quadrant's sign, and extend all six functions to any point on any circle.A Point on a Circle
4 lessons4Standard Position
3 lessons3Coterminal Angles
4 lessons4Radians
6 lessons615Arc Length and Sector Area
5 lessons520The Unit Circle
5 lessons510Reference Angles and Signs
6 lessons620All Four Quadrants
6 lessons625Tangent on the Circle
5 lessons520Six Functions, Any Circle
5 lessons520Final Challenges
6 lessons630Section 3
Graphs of Trig Functions
Start sectionStartDraw sine, cosine and tangent waves and read their equations: amplitude, period, midline and phase shift, in radians and in degrees, then model Ferris wheels, daylight, tides and springs with them.From Circle to Wave
4 lessons4The Cosine Graph
4 lessons4Amplitude
5 lessons520Period
5 lessons515Midline
4 lessons415Phase Shift
5 lessons520Reading a Graph
5 lessons515The Tangent Graph
5 lessons410Modelling with Waves
6 lessons625Final Challenges
6 lessons625Section 4
Trig Identities
Start sectionStartProve identities on the board, one named step at a time: Pythagorean, reciprocal and quotient identities, even, odd and cofunctions, sum and difference, double and half angles, power reduction and product to sum. Find exact values such as sin 15° and tan 105°, and draw sin²x as the wave it is.Identities on the Circle
3 lessons3Reciprocal and Quotient
3 lessons3Pythagorean Identities
4 lessons4Even, Odd and Cofunctions
5 lessons510Proving Identities
6 lessons615Sum and Difference
6 lessons615Double-Angle Formulas
6 lessons625Half Angles, Power Reduction
5 lessons515Product to Sum
4 lessons415Final Challenges
6 lessons630Section 5
Trig Equations and Inverses
Start sectionStartSolve trig equations on an interval and for every solution, exactly and rounded: inverse functions and their ranges, compositions read off a triangle, multiple angles, factoring, and equations that need an identity first.Your First Trig Equations
3 lessons3Inverses and Their Ranges
4 lessons4Evaluating Inverse Trig
3 lessons3Compositions
5 lessons520Equations on a Domain
5 lessons515Off the Special Angles
6 lessons65General Solutions
5 lessons515Multiple Angles
5 lessons515Factoring Trig Equations
6 lessons615Identities First
5 lessons510Final Challenges
5 lessons525Section 6
Triangles Without Right Angles
Start sectionStartSolve any triangle, right angle or not: the law of sines for two angles and a side, the ambiguous case with zero, one or two triangles, the law of cosines for two sides and the angle between or three sides, choosing the law, the area with a sine, Heron's formula, and bearings.Across the Lake
4 lessons4The Ambiguous Case
4 lessons4Law of Cosines: SAS
5 lessons510Law of Cosines: SSS
4 lessons4Which Law to Use
4 lessons45Area of a Triangle
6 lessons620Bearings and Navigation
5 lessons55Final Challenges
5 lessons520
Learn by Solving
Work every problem yourself on an interactive board. Each step is a move you choose, every line is checked, and graphs are drawn by hand.
Solving is a game of legal moves. You pick the move; every line follows from the one before it.
Build Your Math Streak
Stay consistent and watch your progress grow! Track your daily math habit, protect your streak with freeze days, and earn rewards for showing up every day.
12 days streak
Return tomorrow to keep your streak!
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Double or Nothing
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You're Not Alone
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Promotion zoneEvery way to learn
Read, listen, test yourself, ask the AI about your own steps, or look up anything you've already covered. Every lesson meets you where you are.
An equation is a claim: the two sides name the same number. The equals sign asserts sameness, it gives no orders.
A solution is a value of the unknown that makes the claim true. Substitute it and both sides agree.
Solving means changing the form without changing the claim: the same move applied to both sides keeps the balance.
Earn a Certificate
Earn a certificate when you complete a section. Add it to your LinkedIn profile to show how far your math has come.
Certificate of Completion
Math Fundamentals
Add to LinkedInWhy learn trigonometry with Coddy
- You pick the ratio. Tap the sides of a triangle, choose sin, cos, tan or a law, then solve and round.
- The unit circle and graphs by hand. Place angles on the circle and drag waves into shape, and the check reads what you placed.
- Proofs one move at a time. Pick an identity for each step, and the board accepts only a line that follows.
- Free certificate of completion you can share on LinkedIn or your resume. It's proof you finished an interactive Trigonometry course, not just watched videos.
Frequently asked questions about trigonometry
What is trigonometry?
The math of angles and the sides they connect: right triangles first, then every angle on the unit circle, then the waves they make.
Is trigonometry hard?
It is mostly new ideas, not harder algebra. Each lesson adds one step, and the board shows a mistake the moment you make it.
What grade is trigonometry taught in?
In the US, right-triangle trigonometry usually comes in Geometry and the unit circle in Algebra 2 or Precalculus, around grades 10 and 11.
What should I know before learning trigonometry?
How to solve an equation and the Pythagorean theorem. Coddy's Algebra and Geometry courses cover both.
Is the trigonometry course free?
Yes, every lesson and problem is free. Pro removes the daily limit and adds unlimited help from the AI tutor.
Do I get a Trigonometry certificate when I finish?
Yes. When you complete the Trigonometry course you receive a free certificate of completion that you can share on LinkedIn or add to your resume.
