Math Problem Statement

Find the equation of a line passing through the point (-4,3) with slope 1/2. Write the equation of the line passing through the points (1, -1) and (3, 5). Find the angle between the lines obtained in (i) and (ii).

Solution

The image contains the following questions:

  1. Find the equation of a line passing through the point (-4, 3) with slope 12\frac{1}{2}.
  2. Write the equation of the line passing through the points (1, -1) and (3, 5).
  3. Find the angle between the lines obtained in (i) and (ii).

Solutions:

(i) Equation of a line through (-4, 3) with slope 12\frac{1}{2}:

The slope-intercept form of a line is: yy1=m(xx1)y - y_1 = m(x - x_1) Substitute m=12m = \frac{1}{2}, x1=4x_1 = -4, and y1=3y_1 = 3: y3=12(x+4)y - 3 = \frac{1}{2}(x + 4) y3=12x+2y - 3 = \frac{1}{2}x + 2 y=12x+5y = \frac{1}{2}x + 5

The equation of the line is: y=12x+5y = \frac{1}{2}x + 5


(ii) Equation of the line passing through (1, -1) and (3, 5):

First, calculate the slope (mm) of the line: m=y2y1x2x1=5(1)31=62=3m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{5 - (-1)}{3 - 1} = \frac{6}{2} = 3 Using the slope-intercept form, take one point, say (1, -1), and substitute m=3m = 3, x1=1x_1 = 1, y1=1y_1 = -1: y(1)=3(x1)y - (-1) = 3(x - 1) y+1=3x3y + 1 = 3x - 3 y=3x4y = 3x - 4

The equation of the line is: y=3x4y = 3x - 4


(iii) Angle between the lines:

The slopes of the lines are:

  • Line (i): m1=12m_1 = \frac{1}{2}
  • Line (ii): m2=3m_2 = 3

The formula for the angle θ\theta between two lines is: tanθ=m2m11+m1m2\tan\theta = \left| \frac{m_2 - m_1}{1 + m_1m_2} \right| Substitute m1=12m_1 = \frac{1}{2} and m2=3m_2 = 3: tanθ=3121+123\tan\theta = \left| \frac{3 - \frac{1}{2}}{1 + \frac{1}{2} \cdot 3} \right| tanθ=62121+32\tan\theta = \left| \frac{\frac{6}{2} - \frac{1}{2}}{1 + \frac{3}{2}} \right| tanθ=5252=1\tan\theta = \left| \frac{\frac{5}{2}}{\frac{5}{2}} \right| = 1 θ=tan1(1)=45\theta = \tan^{-1}(1) = 45^\circ

The angle between the lines is: 4545^\circ


Summary of Answers:

  1. Equation of line: y=12x+5y = \frac{1}{2}x + 5
  2. Equation of line: y=3x4y = 3x - 4
  3. Angle between lines: 4545^\circ

Let me know if you want further explanation or have questions! Here are related questions to deepen understanding:

  1. What are the general steps to derive the slope-intercept form of a line?
  2. How is the slope calculated for two given points?
  3. What are the special cases when the angle between two lines is 9090^\circ or 00^\circ?
  4. How would the equations change if the points or slope were different?
  5. Can the angle between two lines exceed 9090^\circ? Why or why not?

Tip: When working with angles between lines, remember that the slopes must be consistent with the orientation of the lines.

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Math Problem Analysis

Mathematical Concepts

Equation of a line
Slope-intercept form
Angle between two lines

Formulas

y - y1 = m(x - x1)
m = (y2 - y1) / (x2 - x1)
tan(θ) = |(m2 - m1) / (1 + m1 * m2)|

Theorems

Slope-intercept theorem
Angle calculation between two lines

Suitable Grade Level

Grade 10-12