program for finding power factor using timers and interrupts

I have two sine waves of unknown frequency with peak to peak value around 1.5V....how to write a program using timers to get power factor

how to write a program using timers to get power factor

Use the IDE. Hunt and peck as required. Only you have any clue how you think you will use a timer to get a power factor.

Try here

(How is this a programming question?)