Many students like to use the phrase “All Students Take Calculus” to help them remember where the various trig functions are positive or negative. Place the letters of these four words in quadrants I to IV as shown below.
- The A in Quadrant I stands for “all functions” (sine, cosine & tangent) are positive in this quadrant.
- The S in Quadrant II stands for “only sine” is positive in this quadrant.
- The T in Quadrant III stands for “only tangent” is positive in this quadrant.
- The C in Quadrant IV stands for “only cosine” is positive in this quadrant.
Another simple method is to remember that the cosine values are the x coordinates on the unit circle (and therefore positive in Quadrants I and IV) and the sine values are the y coordinates (and therefore positive in Quadrants I and II).
