# Phasor to Time Domain Math

Mark Zhu
Homework Statement:
See image attachment
Relevant Equations:
I(d, t) = Re[I (d) e ^ jωt]
This is a problem about converting from the phasor to time domain. I am having trouble following the math that the textbook is doing.
I was thinking the final answer should be:
i(d, t) = 0.20 cos(ωt + βd + 159◦) - 0.091 cos(ωt − βd + 185.6◦)
emphasize the minus 0.091 instead of plus 0.091 as shown in the image attachment and textbook.
Am I missing something here? Thank you.

#### Attachments

• 1.PNG
20 KB · Views: 44