Answer: 2cos θ.
- A 2i sin θ
- B cos θ
- C 2
- D 2cos θ
Correct answer: D. 2cos θ
Explanation: 1/z = cos theta - i sin theta (since |z|=1 so 1/z = z-bar). z + 1/z = 2cos theta.
A complex number z = a+ib is plotted as a point (or vector from the origin) on the Argand plane, with the real part along the horizontal axis and the imaginary part along the vertical; its modulus |z| is the vector's length, and its argument θ is the angle from the positive real axis.
Concept context
Complex numbers in a+ib form, modulus, argument, polar form, cube roots of unity, and quadratic equations with complex roots
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