Q. Find the argument of the complex number −33+9i in the interval 0≤θ<2π. Express your answer in terms of π.Answer:
Identify parts of complex number: To find the argument of a complex number in the form a+bi, where a is the real part and b is the imaginary part, we use the formula θ=arctan(ab). However, since the arctan function only gives values from −2π to 2π, we need to consider the quadrant in which the complex number lies to find the correct argument in the interval 0 \leq \theta < 2\pi.
Calculate principal value of argument: First, identify the real part a and the imaginary part b of the complex number −33+9i. Here, a=−33 and b=9.
Consider quadrant for correct argument: Next, calculate the arctan(ab) to find the principal value of the argument. However, since a is negative and b is positive, the complex number lies in the second quadrant. In the second quadrant, the argument θ is π−arctan(∣∣ab∣∣).
Compute absolute value of b/a: Compute the absolute value of b/a: ∣ab∣=∣(−33)9∣=∣3−3∣=∣−3∣.
Calculate arctan(−3): Now, calculate arctan(∣−3∣). Since arctan(3) is known to be 3π, arctan(−3) will also be −3π.
Determine argument in second quadrant: Since the complex number is in the second quadrant, the argument θ is π−(−π/3), which simplifies to π+π/3.
Find argument in interval 0 to 2π: Add π and π/3 to find the argument of the complex number in the interval 0 \leq \theta < 2\pi: θ=π+π/3=(3π/3)+(π/3)=4π/3.
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