find ALL solutions to x^4 + 81 = 0 in trig form

[qubanz10]

so in trig form x^4 = 81CIS180°
x=(4throot 81) CIS (180°/4 +360°k/4)
x= 3CIS(45°+90°k)

if someone could verify i did this right or not. thanks
this is the last one today i promise.

 

[pka]

so in trig form x^4 = 81CIS180°
x=(4throot 81) CIS (180°/4 +360°k/4)
x= 3CIS(45°+90°k)
if someone could verify i did this right or not. thanks
this is the last one today i promise.

You are correct as far as you went. You should that $\displaystyle k=0.~1,~2,~3$