This is the question from a very important assignment I am working on: "A load is being driven by an AC source. At a particular time, the voltage across the load is 120cos(wt+50) and the current through the load is 20sin(wt-10). Calculate the average power in Watts dissipated by the load."
My working: I first convert the current into cosine to give 20cos(wt-100)
Then I use the formula \$\ P=|Vrms||Irms|cos(\theta v -\theta i)\$ which gives me -1039.2 W
I assumed that the question asked for real power since it is the power dissipated in the resistor and thats the only equation the literature gave. An online calculator gave me a complex number with the real part twice the value that I found. Is this correct? Negative power in a resistor? Where did I go wrong?