Question 1072041
{{{r^2=a^2+b^2}}}
{{{r^2=81/16+243/16}}}
{{{r^2=324/16}}}
{{{r=18/4}}}
{{{r=9/2}}}
Recognize that theta is in QII (cos negative, sin positive).
Recognize also that {{{cos(theta)+i*sin(theta)}}} is the required form.