Question 1062350
{{{ Z = Z1*Z2/ (Z1+Z2) }}} = 
{{{ (1+j5)(12+j3) / (1+j5+12+j3) }}} =
{{{ (12+j3+j60+j^2(15)) / (13+j8) }}}  =
{{{ (-3+j63)/(13+j8) }}} =
{{{ (-3+j63)*(13-j8) / ((13+j8)*(13-j8)) }}} =
{{{ (-39+j24+j819-j^2(504)) / (169-j^2(64)) }}} =
{{{  (465+j843) / (233) }}}     (rectangular form with integers)  =
{{{  Z = 1.9957 + j3.618 }}}  (rectangular form)

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Polar form:    {{{ r=sqrt(1.9957^2+3.618^2) = 4.1319 }}}
                    {{{ theta = arccos(1.9957/4.1319) = 61.12^o }}}
                    {{{ Z = 4.1319 }}} /_  {{{ 61.12^o }}}    (polar form, where /_ means "at angle")
                  
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For reference  Z = r/_theta = r*e^(j*theta) = r*(cos (theta) + j*sin (theta))