Hi I need help for the following question,
1.) Let Z1 = 2cis(pi/6) and z2 = rcis(delta) where r>0, and 0<=delta<2pi.
FInd the range of values of r and delta for which z1z2 is
a.) a real number greater than 5
For the modulus of z1z2, I got r>5/2, which was right.
However for the delta, I'm not sure how I'm supposed to do it, it is (pi/6) + delta >5 and then solve the inequality? Seems wrong..
b.) a purely imaginary number with modulus less than 1
How do I find the imaginary number?
Thank you so much for your time, I really appreciate it!
J.
But why is it that when you want a positive real number, it has to be 2kpi?
I think I kind of understand..
Does that meant that the angle has to be in the positive direction to get a positive real number hence 2kpi, not -2kpi or anything?