Question 38 of 70intermediate🔧 ApplyShort Answer3 marks

Find angles between the lines 3x+y=1\sqrt{3}x + y = 1 and x+3y=1x + \sqrt{3}y = 1.

Correct Answer

The angles between the lines are 30° and 150°.

Exercise: EXERCISE 9.3 | Q: 8 | (Page 17)
For More Understanding

Explanation

To find the angle between two lines, we need to find their slopes first and then apply the formula for angle between two lines. The context shows examples of finding slopes from line equations and working with angles in coordinate geometry problems.

Solution Steps

  1. Step 1: Find the slope of the first line. From 3\sqrt{3}x + y = 1, we get y = -3\sqrt{3}x + 1. Therefore, slope m₁ = -3\sqrt{3}.

  2. Step 2: Find the slope of the second line. From x + 3\sqrt{3}y = 1, we get y = (-1/3\sqrt{3})x + 1/3\sqrt{3}. Therefore, slope m₂ = -1/3\sqrt{3}.

  3. Step 3: Apply the formula for angle between two lines: tan θ = |(m₁ - m₂)/(1 + m₁m₂)|

  4. Step 4: Calculate m₁ - m₂ = -3\sqrt{3} - (-1/3\sqrt{3}) = -3\sqrt{3} + 1/3\sqrt{3} = -2/3\sqrt{3}

  5. Step 5: Calculate m₁m₂ = (-3\sqrt{3})(-1/3\sqrt{3}) = 1, so 1 + m₁m₂ = 2

  6. Step 6: Therefore, tan θ = |-2/3\sqrt{3} ÷ 2| = 1/3\sqrt{3}

  7. Step 7: Since tan θ = 1/3\sqrt{3}, we get θ = 30°

  8. Step 8: The angles between two intersecting lines are θ and (180° - θ), so the angles are 30° and 150°.