Math Problem Statement

Determine the angle between the lines passing through the given points, round your answer to the nearest hundredth if necessary:

Line A passes through points: (-2, -7) and (1, -9) Line B passes through points: (5, -1) and (8, 3)

Solution

To determine the angle between the two lines, we first need to calculate the slopes of each line.

Step 1: Calculate the slope of Line A

The slope of a line passing through two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is given by:

m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1}

For Line A, which passes through the points (2,7)(-2, -7) and (1,9)(1, -9):

mA=9(7)1(2)=9+71+2=23m_A = \frac{-9 - (-7)}{1 - (-2)} = \frac{-9 + 7}{1 + 2} = \frac{-2}{3}

So, the slope of Line A, mAm_A, is 23-\frac{2}{3}.

Step 2: Calculate the slope of Line B

For Line B, which passes through the points (5,1)(5, -1) and (8,3)(8, 3):

mB=3(1)85=3+13=43m_B = \frac{3 - (-1)}{8 - 5} = \frac{3 + 1}{3} = \frac{4}{3}

So, the slope of Line B, mBm_B, is 43\frac{4}{3}.

Step 3: Use the formula for the angle between two lines

The angle θ\theta between two lines with slopes m1m_1 and m2m_2 is given by:

tan(θ)=m1m21+m1m2\tan(\theta) = \left|\frac{m_1 - m_2}{1 + m_1m_2}\right|

Substituting mA=23m_A = -\frac{2}{3} and mB=43m_B = \frac{4}{3}:

tan(θ)=23431+(23)(43)\tan(\theta) = \left|\frac{-\frac{2}{3} - \frac{4}{3}}{1 + \left(-\frac{2}{3}\right)\left(\frac{4}{3}\right)}\right|

Simplifying the expression:

tan(θ)=63189=219=181=18\tan(\theta) = \left|\frac{-\frac{6}{3}}{1 - \frac{8}{9}}\right| = \left|\frac{-2}{\frac{1}{9}}\right| = \left|-\frac{18}{1}\right| = 18

Step 4: Calculate the angle θ\theta

Now, we take the arctan (inverse tangent) to find the angle:

θ=arctan(18)\theta = \arctan(18)

Using a calculator:

θ86.82\theta \approx 86.82^\circ

Final Answer:

The angle between the two lines is approximately 86.82 degrees.

Would you like more details on any part of the solution?

Here are five related questions you might find interesting:

  1. How do you calculate the angle between two lines that are perpendicular?
  2. What is the significance of the angle between two intersecting lines?
  3. How do you find the slope of a line parallel to a given line?
  4. What is the equation of a line that passes through a given point and has a specific slope?
  5. How does changing one point on a line affect the slope and angle?

Tip: When dealing with angles between lines, a small change in slope can lead to a large change in the resulting angle.

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Math Problem Analysis

Mathematical Concepts

Analytic Geometry
Slopes of Lines
Angle Between Two Lines

Formulas

Slope of a line: m = (y2 - y1) / (x2 - x1)
Angle between two lines: tan(θ) = |(m1 - m2) / (1 + m1 * m2)|

Theorems

Tangent Formula for Angle Between Two Lines

Suitable Grade Level

Grades 9-12