Question 761600:  What is the square root of -7+8i 
 Answer by stanbon(75887)      (Show Source): 
You can  put this solution on YOUR website! What is the square root of -7+8i 
------ 
Use polar notation: 
r = sqrt[7^2 + 8^2] = 10.83 
theta = arctan(-8/7) = 131.2 degrees 
----- 
-7+8i = 10.83cis(131.2) 
----- 
sqrt(-7+8i) = sqrt(10.83)cis[(131.2+360n)/2] 
--- 
If n = 0 you get sqrt(10.83)cis(65.6 degrees) 
If n = 1 you get sqrt(10.83)cis(245.50 degrees) 
---- 
Convert to rectangular notation: 
sqrt = 3.29[cos(65.5)+isin(65.5)] = 1.36 + 3i 
sqrt = 3.29[cos(245.5)+isin(245.5)] = -1.36 -3i 
================================================== 
Cheers, 
Stan H. 
  | 
 
  
 
 |   
 
 |