The argument of a complex number

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SUMMARY

The argument of a complex number can be calculated using geometric principles without a calculator. For the complex number z = 1 + sqrt(3)*i, the absolute value |z| is determined as the hypotenuse of a right triangle formed by its real and imaginary components. By applying the Pythagorean theorem, the argument is found to be arg(z) = π/3, which is confirmed as correct. This method effectively utilizes trigonometric relationships to derive the angle from the positive real axis.

PREREQUISITES
  • Understanding of complex numbers and their representation in the Cartesian plane
  • Knowledge of the Pythagorean theorem
  • Familiarity with trigonometric functions, specifically sine and cosine
  • Basic skills in geometry, particularly in calculating angles
NEXT STEPS
  • Study the geometric interpretation of complex numbers in the Argand plane
  • Learn about the polar form of complex numbers and how to convert between rectangular and polar coordinates
  • Explore the use of trigonometric identities to derive angles in complex number calculations
  • Investigate other methods for calculating the argument of complex numbers, such as using the arctangent function
USEFUL FOR

Students studying complex analysis, mathematicians, and anyone interested in mastering the geometric interpretation of complex numbers and their properties.

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Homework Equations



I was just wondering, how do you guys get the argument value from a complex number
without using any calculator, i know that some solutions may be impossible to get without
a calculator but just finding some of the easier angles.



The Attempt at a Solution



Example: If i have the following complex number

z = 1 + sqrt(3)*i

i calculate the absolute value of z (|z|) and since that value is the distance from the origin
to the point (r) i put the value as the hypotenuse of a triangle and apply the x and the y values to the adjecent and the opposite and now i try to find the argument of z.

I use the pythagorean theorem to get the angle of the argument and i get the answer arg(z) = pi / 3 which happens to be true in this case. I'm just wondering if this is the right approach to this problem or if there exist any other probably better solutions for finding the argument of z without the use of a calculator.

//Thx in advance
 
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Well that is how you get arg(z). It is the angle measured from the positive real axis to the complex number.
 

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