Question

What is an angle between 0 and 2pi that is coterminal with -9pi/4?

Answer 1

`(7pi)/4`

Explanation:

Keep adding a full rotation until you get a coterminal angle in your interval `[0, 2pi]`

`(-9pi)/4+(8pi)/4=(-pi)/4` (Close! Not there yet, though...)

`(-pi)/4+(8pi)/4=(7pi)/4` Between `[0, 2pi]`! Done!