How to use this course
Follow the topics in order
Each topic teaches one piece of the mathematics and prepares you for the next. Start with Topic 1 if angles or the unit circle are new to you. Return here at any time to reopen a topic or continue from the last one you visited.
Part 1
Angle foundations
- What an Angle RepresentsBuild the idea of an angle as a directed rotation between two rays. Open topic
- Standard PositionPlace an angle at the origin with its initial side on the positive x-axis. Open topic
- Positive and Negative RotationUse counterclockwise and clockwise motion to determine the sign of an angle. Open topic
- Quadrants and Quadrantal AnglesLocate terminal sides in quadrants and recognize angles that end on an axis. Open topic
- Coterminal AnglesGenerate and interpret angles that finish on the same terminal side. Open topic
Part 2
Radians and conversions
- Circle Vocabulary and Arc LengthConnect radius, circumference, central angle, and intercepted arc length. Open topic
- What a Radian RepresentsUnderstand one radian through the relationship between radius and arc length. Open topic
- Degree and Radian LandmarksLearn the degree and radian measures for the circle's major landmarks. Open topic
- Converting Degrees to RadiansConvert degree measures exactly and simplify the resulting fractions of pi. Open topic
- Converting Radians to DegreesConvert radian measures to degrees by canceling units deliberately. Open topic
Part 3
Building the unit circle
- Unit-Circle CoordinatesConnect an angle's terminal point with its ordered pair on the unit circle. Open topic
- The Pythagorean RelationshipUse x² + y² = 1 to reason about every point on the unit circle. Open topic
- Deriving 45° CoordinatesDerive the exact 45° unit-circle coordinates from an isosceles right triangle. Open topic
- Deriving 30° and 60° CoordinatesDerive exact coordinates from a 30-60-90 triangle instead of memorizing them blindly. Open topic
- Reference AnglesFind the acute angle between a terminal side and the x-axis in every quadrant. Open topic
- Coordinate Signs by QuadrantDetermine the signs of x and y from the terminal side's quadrant. Open topic
Part 4
Exact trigonometric values
- Defining Cosine as the x-CoordinateRead cosine as the horizontal coordinate of a unit-circle point. Open topic
- Defining Sine as the y-CoordinateRead sine as the vertical coordinate of a unit-circle point. Open topic
- Evaluating Sine ExactlyCombine reference angles and quadrant signs to evaluate sine exactly. Open topic
- Evaluating Cosine ExactlyCombine reference angles and quadrant signs to evaluate cosine exactly. Open topic
- Evaluating Multi-Turn and Radian AnglesReduce multi-turn degree and radian angles before evaluating sine or cosine. Open topic