Math Problem Statement

find min value of arg z when modulus of z+1-1*root3 = 1

Solution

To solve this problem, let us denote zz as a complex number, which we can write as:

z=x+yiz = x + yi

where xx and yy are real numbers, and ii is the imaginary unit. The given condition is:

z+1i3=1|z + 1 - i\sqrt{3}| = 1

This represents the modulus (distance from the origin) of the complex number z+1i3z + 1 - i\sqrt{3}. We can rewrite this in the form of:

(x+1)+(y3)i=1|(x + 1) + (y - \sqrt{3})i| = 1

This expression represents the distance from the point (1,3)(-1, \sqrt{3}) to the point (x,y)(x, y), and it is equal to 1. Hence, (x,y)(x, y) lies on a circle centered at (1,3)(-1, \sqrt{3}) with radius 1.

To find the minimum value of arg(z)\arg(z), which represents the angle θ\theta that zz makes with the positive real axis, we need to think geometrically about the position of the circle and the angles involved.

Step-by-Step Approach:

  1. Identify the Circle's Center and Radius:
    The center of the circle is at (1,3)(-1, \sqrt{3}), and the radius is 11.

  2. Find the Argument:
    The argument of zz is the angle between the line from the origin (0,0)(0, 0) to the point (x,y)(x, y) on the circle and the positive real axis.

  3. Geometric Interpretation:
    The minimum value of the argument will occur when the line from the origin to the point on the circle is closest to the positive real axis. This means we want to find the line that is tangent from the origin to the circle.

  4. Using Geometry to Find the Minimum Argument:

    • The center of the circle is (1,3)(-1, \sqrt{3}).

    • The radius is 11.

    • The distance from the origin to the center is:

      d=(1)2+(3)2=1+3=2d = \sqrt{(-1)^2 + (\sqrt{3})^2} = \sqrt{1 + 3} = 2

    • Since the radius is 11 and the distance from the origin to the center is 22, we can use trigonometry to find the minimum argument. The angle between the line from the origin to the center and the tangent line is given by:

      sin(θ)=radiusdistance from origin to center=12\sin(\theta) = \frac{\text{radius}}{\text{distance from origin to center}} = \frac{1}{2}

      Therefore:

      θ=sin1(12)=π6\theta = \sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6}

Conclusion:

The minimum value of the argument arg(z)\arg(z) is π6\boxed{\frac{\pi}{6}}.

Would you like me to explain any part of this solution in more detail, or do you have any further questions?

Here are 5 related questions to expand on this topic:

  1. How do you calculate the modulus of a complex number?
  2. What is the geometric representation of complex numbers in the Argand plane?
  3. How can you determine the argument of a complex number given its Cartesian form?
  4. What are some methods to find the distance between two points in the complex plane?
  5. How do you determine if a complex number lies on a specific circle?

Tip: When solving problems involving modulus and arguments of complex numbers, drawing a diagram on the Argand plane can often provide clear geometric insight.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Modulus
Argument of a Complex Number
Geometry of Complex Numbers

Formulas

|z + 1 - i√3| = 1
Distance formula: d = √[(x2 - x1)^2 + (y2 - y1)^2]
Sine rule: sin(θ) = opposite/hypotenuse

Theorems

Geometric Interpretation of Complex Numbers
Trigonometric Theorem (Sine rule)

Suitable Grade Level

Grades 11-12 (Advanced High School Level)