Question 390567
<pre><b>
{{{2=r*cos(theta+"180°")}}}

Use the identity {{{cos(theta+"180°")=-cos(theta)}}}

{{{2=r(-cos(theta))}}}

{{{2=-r*cos(theta)}}}

Change it from polar to rectangular form, using substitution {{{cos(theta)=x/r}}}

{{{2=-r(x/r)}}}

{{{2=-cross(r)(x/cross(r))}}}

{{{2=-x}}}

{{{x=-2}}}

{{{drawing(200,200,-5,5,-5,5, graph(200,200,-5,5,-5,5), line(-2,6,-2,-6))}}}

Edwin</pre>