Understanding Complex Plane and Finding Arguments: A Scientist's Perspective

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SUMMARY

The discussion centers on the complexities of finding arguments in the context of trigonometric identities, specifically using the equations cos2x = 1 - 2sinx and sin2x = 2sinxcosx. A participant encountered difficulties determining the argument, mistakenly concluding that tan(α) = cot(θ), while the correct formulation is tan(α) = -cot(θ). The confusion arises from the negative sign associated with the imaginary component, specifically -sin(2θ), which is crucial for arriving at the correct solution.

PREREQUISITES
  • Understanding of trigonometric identities, specifically sin and cos functions.
  • Familiarity with the Pythagorean theorem as it applies to complex numbers.
  • Knowledge of the relationship between tangent and cotangent functions.
  • Basic comprehension of complex numbers and their representations in the complex plane.
NEXT STEPS
  • Study the derivation of trigonometric identities, focusing on sin(2θ) and cos(2θ).
  • Learn about the properties of complex numbers and their geometric interpretations in the complex plane.
  • Explore the implications of negative signs in trigonometric equations and their effects on arguments.
  • Practice solving problems involving the conversion between tangent and cotangent in various contexts.
USEFUL FOR

Students studying trigonometry, mathematicians exploring complex numbers, and educators seeking to clarify the relationship between trigonometric functions and their arguments.

SUSUSUSUSUSUSUSU

Homework Statement


The picture below.

Homework Equations


cos2x=1-2sinx
sin2x= 2sinxcosx

The Attempt at a Solution



I got the modulus by using the Pythagoras theorem which is 2sin theta

But I faced difficulty to find the argument. I have no idea why i end up with tan a (alpha) = cot theta which is not the right answer. on the answer booklet, it's written that it is tan a = -cot theta. I do not understand that why it comes to negative...? I just did tan a = sin2x/(1-cos2x) = cot x. Is it just because it is -isin2x?I think after that i can solve it.

Thank you.
 

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SUSUSUSUSUSUSUSU said:

Homework Statement


The picture below.

Homework Equations


cos2x=1-2sinx
sin2x= 2sinxcosx

The Attempt at a Solution



I got the modulus by using the Pythagoras theorem which is 2sin theta

But I faced difficulty to find the argument. I have no idea why i end up with tan a (alpha) = cot theta which is not the right answer.
on the answer booklet, it's written that it is tan a = -cot theta. I do not understand that why it comes to negative...? I just did tan a = sin2x/(1-cos2x) = cot x. Is it just because it is -isin2x?
Yes. The imaginary component is ##-\sin(2\theta)##.
SUSUSUSUSUSUSUSU said:
I think after that i can solve it.

Thank you.
 

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