How do you get 2e^(i(9pi/10)) (exponential form), into points to be shown on the argand diagram?

Question

Hey, can you please show me how to do this?

Thanks

Answer 1

Recall that e^iΘ = cos Θ + i sin Θ

so e^i(9π/10) = cos 9π/10 + i sin 9π/10

Now 2 times it  just equals

2cos 9π/10 + 2i sin 9π/10

and that's the rectangular coordinates for 2e^(i(9π/10)