Answer
$3.0642+2.5712i$
Work Step by Step
$4$ cis $40^{\circ}$=$4(\cos40^{\circ}+i\sin40^{\circ})$
Using a calculator, we find that $\cos40^{\circ}=0.76604$ and $\sin40^{\circ}=0.64279$
Substituting these values in the expression and solving:
$4(\cos40^{\circ}+i\sin40^{\circ})=4(0.76604+0.64279i)=3.0642+2.5712i$
