Regions of the Plane — Cheat sheet
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Quadrant sign table
| Quadrant | Signs | Where |
|---|
| I | (+,+) | upper right |
| II | (−,+) | upper left |
| III | (−,−) | lower left |
| IV | (+,−) | lower right |
| Numbered counter-clockwise from the upper right. Axis points belong to no quadrant. | | |
Problem patterns
- Known quadrant → known signs of x and y → sign of any product or sum by sign rules.
- "Point in quadrant N" → two inequalities → intersect the solution sets.
- "Point on y-axis" → set abscissa =0; "on x-axis" → set ordinate =0.
Mr. Integral