How do you multiply eπ8ieπ2i in trigonometric form?

1 Answer
Sep 30, 2016

As eiθ=cosθ+isinθ

eπ8i=cos(π8)+isin(π8) and

eπ2i=cos(π2)+isin(π2)

and eπ8ieπ2i=(cos(π8)+isin(π8))(cos(π2)+isin(π2))

= cos(π8)cos(π2)+cos(π8)×isin(π2)+isin(π8)×cos(π2)+isin(π8)×isin(π2)

= cos(π8)cos(π2)+icos(π8)sin(π2)+isin(π8)cos(π2)+i2sin(π8)sin(π2)

= cos(π8)cos(π2)+icos(π8)sin(π2)+isin(π8)cos(π2)sin(π8)sin(π2)

= [cos(π8)cos(π2)sin(π8)sin(π2)]+i[cos(π2)sin(π8)+sin(π2)cos(π8)]

= cos(π8+π2)+isin(π8+π2)

= eπ8+π2