Explanation
This is a handy acronym to help you remember the CAST Rule for trigonometric functions. Go counterclockwise, starting from the bottom right quadrant of graph axes. Every letter in it stands for one term below.
- C is the area where the angle is positive for Cosine.
- A is the area where the angle is positive for all trigonometric functions.
- S is the area where the angle is positive for Sine.
- T is the area where the angle is positive for Tangent.
Note: always measure from the x-axis to the angle line.