Question 984816
<pre>
{{{5*(cos("150°")+i^""sin("150°"))*4*(cos("30°")+i^""sin("30°"))}}}

Multiply the 5 by the 4 getting 20
Add the 150° and the 30° getting 180°

{{{20*(cos("180°")+i^""sin("180°"))}}}

Then substitute cos(180°) = -1 and sin(180°) = 0, the above becomes

{{{20*(-1+0i)}}}

-20.

Edwin</pre>