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Chasing 100M Daily Users, Duolingo Reconsiders Ads, Paying Influencers, and Its Most Expensive Plan

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Introduction to Using Trigonometric Identities - Precalculus - Trigonometry

A concise introduction to using trigonometric identities, including Pythagorean, reciprocal, and even/odd identities.
- YouTube
- 24 minutes
- Self-Paced
- Free Video
How to Solve Trigonometric Equations - Precalculus - Trigonometry

Solve trigonometric equations through unit-circle relationships without relying on inverse trigonometric functions.
- YouTube
- 1 hour 35 minutes
- Self-Paced
- Free Video
How to Find Inverse Trigonometric Functions - Precalculus - Trigonometry

A step-by-step lesson on finding inverse trigonometric functions and determining their domains and ranges.
- YouTube
- 32 minutes
- Self-Paced
- Free Video
How to Use Inverse Trigonometric Functions - Precalculus - Trigonometry

Learn to use inverse trigonometric functions and understand their relationship to basic trigonometric functions.
- YouTube
- 54 minutes
- Self-Paced
- Free Video
How to Graph Phase Shifts of Trigonometric Functions - Precalculus - Trigonometry

Learn to graph horizontal (phase) shifts of sine and cosine functions and extend the technique to other trigonometric functions.
- YouTube
- 38 minutes
- Self-Paced
- Free Video
How to Graph Cosecant and Secant - Precalculus - Trigonometry

Learn to graph secant and cosecant functions through their relationships to cosine and sine, including transformations.
- YouTube
- 30 minutes
- Self-Paced
- Free Video
Graphing Transformations with Tangent and Cotangent - Precalculus - Trigonometry

Learn to graph tangent and cotangent functions using vertical translations, reflections, amplitude, and period changes.
- YouTube
- 41 minutes
- Self-Paced
- Free Video
Graphing Transformations with Sine and Cosine - Precalculus - Trigonometry

Learn to graph sine and cosine functions, including amplitude, period, vertical shifts, and other transformations.
- YouTube
- 1 hour 7 minutes
- Self-Paced
- Free Video
Pythagorean Identities for Trigonometric Functions

Explains even, odd, and Pythagorean trigonometric identities through the unit circle and their corollaries.
- YouTube
- 38 minutes
- Self-Paced
- Free Video
Reciprocal Identities in Trigonometry - Precalculus - Trigonometry

Learn how reciprocal trigonometric identities work by connecting the unit circle with right-triangle trigonometry.
- YouTube
- 47 minutes
- Self-Paced
- Free Video
Trigonometric Functions and the Unit Circle - Precalculus - Trigonometry

Explores how the unit circle connects right-triangle trigonometry to the creation of trigonometric functions.
- YouTube
- 40 minutes
- Self-Paced
- Free Video
Proof by Mathematical Induction - Precalculus - College Algebra

Learn to prove summation formulas using mathematical induction.
- YouTube
- 23 minutes
- Self-Paced
- Free Video
Geometric Series - Precalculus - College Algebra

Learn to calculate partial sums of geometric series and determine their infinite sums.
- YouTube
- 42 minutes
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Arithmetic Sequences - Precalculus - College Algebra

Learn to identify and create arithmetic sequences by finding the common difference and first term.
- YouTube
- 22 minutes
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- Free Video
Introduction to Series and Summation Notation

Learn how series arise from sequences and how summation notation and formulas make series calculations efficient.
- YouTube
- 43 minutes
- Self-Paced
- Free Video

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