🌿🌿👉👉QUADRANT RULES👈👈💚💚
The **Quadrant Rule** in math refers to the system used to divide the **coordinate plane** into four sections, called **quadrants**, based on the signs of the **x** and **y** coordinates. This is essential in **graphing points, analyzing functions, and trigonometry**.
---
### **The Four Quadrants**
The **xy-plane** is divided by the **x-axis** (horizontal) and **y-axis** (vertical) into four quadrants, labeled **I, II, III, and IV** in **counterclockwise** order:
| Quadrant | \(x\)-coordinate | \(y\)-coordinate | Example Point |
|----------|------------------|------------------|---------------|
| **I** | Positive (+) | Positive (+) | \((3, 4)\) |
| **II** | Negative (−) | Positive (+) | \((-2, 5)\) |
| **III** | Negative (−) | Negative (−) | \((-1, -3)\) |
| **IV** | Positive (+) | Negative (−) | \((6, -2)\) |
- **Axes:** Points on the x-axis (\(y=0\)) or y-axis (\(x=0\)) do not belong to any quadrant.
---
### **Key Rules & Applications**
1. **Signs of Coordinates**
- **Quadrant I:** \((+, +)\)
- **Quadrant II:** \((-, +)\)
- **Quadrant III:** \((-, -)\)
- **Quadrant IV:** \((+, -)\)
2. **Trigonometric Functions (Unit Circle)**
- Angles are measured from the positive x-axis.
- The signs of **sine, cosine, and tangent** depend on the quadrant:
- **Q1:** All \((sin, cos, tan)\) are positive.
- **Q2:** Only \(sin\) is positive.
- **Q3:** Only \(tan\) is positive.
- **Q4:** Only \(cos\) is positive.
*(Mnemonic: **"All Students Take Calculus"** for A, S, T, C.)*
3. **Graphing Equations**
- The quadrant affects the behavior of functions:
- **Linear equations:** Slope determines direction.
- **Parabolas:** Vertex position changes based on coefficients.
4. **Distance & Midpoint Formulas**
- Calculations remain the same, but signs matter for quadrant placement.
---
### **Example Problems**
1. **Identifying Quadrants:**
- \((−5, 1)\) → **Quadrant II** (since \(x < 0, y > 0\)).
- \((4, −7)\) → **Quadrant IV** (since \(x > 0, y < 0\)).
2. **Trigonometry Example:**
- If an angle \(θ\) is in **Quadrant III**, and \(\sin θ = -\frac{3}{5}\), then \(\cos θ\) is also negative (since only \(tan\) is positive in Q3).
---
### **Special Cases**
- **Origin:** \((0, 0)\) is where the axes meet (no quadrant).
- **Boundaries:** Points like \((3, 0)\) lie on the x-axis, not in a quadrant.
---
### **Visualization**
```
y
|
II | I
|
------------------> x
|
III | IV
|
```
Let me know if you'd like deeper explanations on quadrants in graphing, trigonometry, or other applications! 😊
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