SOLUTION: Can you help me convert this to trigonometric form? {{{ z = -9/4 }}}+{{{ 9 sqrt( 3 )/4 }}}i A.) 81/4(sin120 + i cos120) B.) 81/4(cos120 + i sin120) C.) 9/2(cos120 + i sin120) D

Algebra ->  Test -> SOLUTION: Can you help me convert this to trigonometric form? {{{ z = -9/4 }}}+{{{ 9 sqrt( 3 )/4 }}}i A.) 81/4(sin120 + i cos120) B.) 81/4(cos120 + i sin120) C.) 9/2(cos120 + i sin120) D      Log On


   

Question 1072041: Can you help me convert this to trigonometric form? +z+=+-9%2F4+++9+sqrt%28+3+%29%2F4+i
A.) 81/4(sin120 + i cos120)
B.) 81/4(cos120 + i sin120)
C.) 9/2(cos120 + i sin120)
D.) 9/2(cos120 + i sin 90)
Thank you.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
r%5E2=a%5E2%2Bb%5E2
r%5E2=81%2F16%2B243%2F16
r%5E2=324%2F16
r=18%2F4
r=9%2F2
Recognize that theta is in QII (cos negative, sin positive).
Recognize also that cos%28theta%29%2Bi%2Asin%28theta%29 is the required form.