Here’s the easiest way to remember the labels. Start at the top-right (Quadrant I). Then go counter-clockwise. I = (+,+), II = (-,+), III = (-,-), IV = (+,-). It’s an alphabet song of signs.
If you mess up, just remember the word “CAST.” C for Cosine positive, A for All positive, S for Sine positive, T for Tangent positive. (Okay, that’s for trigonometry, but it’s a fun party trick.)
Or just use this: “All Students Take Calculus.” Starts at Quadrant I, goes counter-clockwise. All positive? A in Quadrant I. Students? S in Quadrant II? Yes, it’s a stretch, but it works.
