
Bradford T. answered 12/03/21
Retired Engineer / Upper level math instructor
a)
z = 2eiθ
z1/3 = 21/3eiθ/3 = 21/3(cos1/3(105°)+isin1/3(105°)
b)
r = √(25+9) = √34
tan-1(-3/5) = -30.96 --> θ=360-30.96 ≈ 329° = 1.8278π radians (Quadrant IV)
f(r,θ) = √34(cos(1.8278π)+isin(1.8278π)