Question 36 of 480
Find the tangent to the acute angle between the lines 2x + y = 3 and 3x - 2y = 5.
- A. -7/4
- B. 7/8
- C. 7/4
- D. 7/2
Correct Answer:
C
Explanation
To find the tangent of the acute angle between the two lines given by the equations \(2x + y = 3\) and \(3x - 2y = 5\), we will follow a systematic approach.
### Step 1: Find the slopes of the lines
First, we need to rewrite both equations in the slope-intercept form \(y = mx + b\), where \(m\) is the slope.
**For the first line \(2x + y = 3\):**
1. Rearranging gives:
\[
y = -2x + 3
\]
Here, the slope \(m_1 = -2\).
**For the second line \(3x - 2y = 5\):**
1. Rearranging gives:
\[
-2y = -3x + 5 \quad \Rightarrow \quad y = \frac{3}{2}x - \frac{5}{2}
\]
Here, the slope \(m_2 = \frac{3}{2}\).
### Step 2: Use the formula for the tangent of the angle between two lines
The formula for the tangent of the angle \(\theta\) between two lines with slopes \(m_1\) and \(m_2\) is given by:
\[
\tan(\theta) = \left| \frac{m_1 - m_2}{1 + m_1 m_2} \right|
\]
### Step 3: Substitute the slopes into the formula
Now we substitute \(m_1 = -2\) and \(m_2 = \frac{3}{2}\) into the formula:
1. Calculate \(m_1 - m_2\):
\[
m_1 - m_2 = -2 - \frac{3}{2} = -\frac{4}{2} - \frac{3}{2} = -\frac{7}{2}
\]
2. Calculate \(1 + m_1 m_2\):
\[
m_1 m_2 = -2 \cdot \frac{3}{2} = -3 \quad \Rightarrow \quad 1 + m_1 m_2 = 1 - 3 = -2
\]
### Step 4: Substitute into the tangent formula
Now we substitute these values into the tangent formula:
\[
\tan(\theta) = \left| \frac{-\frac{7}{2}}{-2} \right| = \left| \frac{7}{2} \cdot \frac{1}{-2} \right| = \left| \frac{7}{-4} \right| = \frac{7}{4}
\]
### Conclusion: Identify the correct option
The tangent of the acute angle between the two lines is \(\frac{7}{4}\). Therefore, the correct option is:
**C. 7/4**
### Explanation of Other Options
- **Option A: -7/4** - This is incorrect because the tangent of an angle cannot be negative when considering the acute angle between two lines.
- **Option B: 7/8** - This is incorrect as it does not match our calculated value of \(\frac{7}{4}\).
- **Option D: 7/2** - This is also incorrect as it is not the result of our calculations.
### Revision Summary
- To find the tangent of the angle between two lines, first determine their slopes.
- Use the formula \(\tan(\theta) = \left| \frac{m_1 - m_2}{1 + m_1 m_2} \right|\).
- Substitute the slopes into the formula to find the tangent value.
- The correct answer for the tangent of the acute angle between the lines is \(\frac{7}{4}\).