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Grade 11Analytical Geometry

A straight line L through the point (3, -2) is inclined at an angle 60° to the line 3x + y = 1 . If L also intersects the x-axis, then the equation of L is

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12 Years agoGrade 11
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ApprovedApproved Tutor Answer11 Months ago

To find the equation of the line L that passes through the point (3, -2) and is inclined at an angle of 60° to the line given by the equation 3x + y = 1, we can follow a systematic approach. First, we need to determine the slope of the line represented by the equation 3x + y = 1, and then use the angle information to find the slope of line L.

Finding the Slope of the Given Line

The equation of the line can be rewritten in slope-intercept form (y = mx + b) to easily identify its slope. Starting from the original equation:

  • 3x + y = 1
  • y = -3x + 1

From this, we see that the slope (m) of the line is -3.

Calculating the Slope of Line L

Line L is inclined at an angle of 60° to the line with a slope of -3. To find the slope of line L (let's call it m_L), we can use the formula for the tangent of the angle between two lines:

  • tan(θ) = |(m_L - m_1) / (1 + m_L * m_1)|

Here, m_1 is the slope of the given line (-3), and θ is 60°. The tangent of 60° is √3. Plugging in the values:

  • √3 = |(m_L + 3) / (1 - 3m_L)|

We can solve this equation for m_L. First, we consider two cases due to the absolute value.

Case 1: m_L + 3 = √3(1 - 3m_L)

Expanding and rearranging gives:

  • m_L + 3 = √3 - 3√3m_L
  • (1 + 3√3)m_L = √3 - 3
  • m_L = (√3 - 3) / (1 + 3√3)

Case 2: m_L + 3 = -√3(1 - 3m_L)

Similarly, we expand and rearrange:

  • m_L + 3 = -√3 + 3√3m_L
  • (1 - 3√3)m_L = -√3 - 3
  • m_L = (-√3 - 3) / (1 - 3√3)

Finding the Equation of Line L

Now that we have the slopes, we can use the point-slope form of the line equation, which is:

  • y - y_1 = m(x - x_1)

Substituting the point (3, -2) into the equation:

  • y + 2 = m_L(x - 3)

Finding the Intersection with the X-axis

To find where line L intersects the x-axis, we set y = 0:

  • 0 + 2 = m_L(x - 3)
  • 2 = m_L(x - 3)
  • x = 3 + 2/m_L

We can substitute the values of m_L from both cases to find the x-intercepts. After calculating, we can determine which slope gives a valid intersection point on the x-axis.

Finalizing the Equation

After substituting the slopes back into the point-slope form and simplifying, we will arrive at the final equation of line L. Depending on the calculations, you will find that the equation will be in the form:

  • y = mx + b

where m is the slope derived from either case and b is the y-intercept calculated from the point (3, -2).

By following these steps, you can derive the equation of line L that meets the specified conditions. If you need further clarification on any of the steps, feel free to ask!