Math Problem Statement

Find the equation of a line making an angle of 120° with X-axis and passing through (2, 3).

Solution

To find the equation of the line that makes an angle of 120120^\circ with the X-axis and passes through the point (2,3)(2, 3), we can proceed as follows:

Step 1: Find the slope of the line

The slope mm of a line that makes an angle θ\theta with the X-axis is given by: m=tan(θ)m = \tan(\theta) Here, θ=120\theta = 120^\circ. So, m=tan(120)m = \tan(120^\circ) Using the tangent of 120120^\circ: tan(120)=tan(18060)=tan(60)\tan(120^\circ) = \tan(180^\circ - 60^\circ) = -\tan(60^\circ) Since tan(60)=3\tan(60^\circ) = \sqrt{3}, we have: m=3m = -\sqrt{3}

Step 2: Use the point-slope form of the equation of a line

The point-slope form of the equation of a line is: yy1=m(xx1)y - y_1 = m(x - x_1) where (x1,y1)(x_1, y_1) is a point on the line and mm is the slope. Here, (x1,y1)=(2,3)(x_1, y_1) = (2, 3) and m=3m = -\sqrt{3}.

Substitute the values: y3=3(x2)y - 3 = -\sqrt{3}(x - 2)

Step 3: Simplify the equation

Expand and simplify the equation: y3=3x+23y - 3 = -\sqrt{3}x + 2\sqrt{3} y=3x+23+3y = -\sqrt{3}x + 2\sqrt{3} + 3

Thus, the equation of the line is: y=3x+(23+3)y = -\sqrt{3}x + (2\sqrt{3} + 3)

Let me know if you need further clarifications.

Related Questions:

  1. What is the equation of a line passing through the origin and making an angle of 4545^\circ with the X-axis?
  2. How do you derive the general form of the equation of a line given its slope and a point?
  3. What happens to the slope if the angle made with the X-axis is 9090^\circ?
  4. How do you find the equation of a line perpendicular to the line obtained here?
  5. How can we check if two lines are parallel based on their equations?

Tip:

Always remember that the slope of a line is negative when the angle with the X-axis is between 9090^\circ and 180180^\circ.

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Math Problem Analysis

Mathematical Concepts

Algebra
Analytic Geometry
Lines and Angles

Formulas

Slope of a line: m = tan(θ)
Point-slope form: y - y1 = m(x - x1)

Theorems

Relationship between slope and angle with the X-axis

Suitable Grade Level

Grades 9-12