Give a complex number z , so ;
a) |z|=π,z≠±π
b) e^z=e^(-1); z ≠ -1
c) ³√z=1+ i
For the third problem:
Use deMoivre's Theorem:
Write the complex number in r[cos(θ) +i·sin(θ)] form: r = √(x²+y²) θ = invTan(y/x)
z = 1 + i ---> x = 1 and y = 1 r = √(1²+1²) ---> r = √2 θ = invTan(1/1) = 45°
z^(1/3) ---> r^(1/3)[cos(θ/3) + ·isin(θ/3) ---> (√2)^(1/3)[cos(45°/3) +i·sin(45°/3)]
---> (2)^(1/6)[cos(15) + isin(15)]
then, add two more values by adding 360°/3 = 120° and 2·360°/3 = 240°
---> (2)^(1/6)[cos(135°) + isin(135°)] and (2)^(1/6)[cos(255°) + isin(255°)]
For the first problem: The absolute value of a complex number is the distance from the origin to that point.
So, if you draw a circle whose center is the origin and whose radius is π, every point on that circle will solve the problem.
The two obvious answers are at x = π and x = -π, but you aren't allowed to use them; so choose any other location on the circle.
If you choose the angle 45°, θ= 45° and r = π,
the value of z = r[cos(θ) + i ·sin(θ)] becomes π[cos(45°) + i · sin(45°)] = √2/2·π + √2/2·π·i
For the third problem:
Use deMoivre's Theorem:
Write the complex number in r[cos(θ) +i·sin(θ)] form: r = √(x²+y²) θ = invTan(y/x)
z = 1 + i ---> x = 1 and y = 1 r = √(1²+1²) ---> r = √2 θ = invTan(1/1) = 45°
z^(1/3) ---> r^(1/3)[cos(θ/3) + ·isin(θ/3) ---> (√2)^(1/3)[cos(45°/3) +i·sin(45°/3)]
---> (2)^(1/6)[cos(15) + isin(15)]
then, add two more values by adding 360°/3 = 120° and 2·360°/3 = 240°
---> (2)^(1/6)[cos(135°) + isin(135°)] and (2)^(1/6)[cos(255°) + isin(255°)]