Question

Find another angle θ between 0∘ and 360∘ that has the same cosine as 225∘. (That is, find θ satisfying cos(θ)=cos(225∘).)

Answer 1

The angle theta that measures 225 degrees is in QIII. It looks like this:

Answer 2

That reference angle is a 45 degree angle. Do you know the sides for that type of triangle?

Answer 3

Actually that reference angle is a -45 degree angle if it is measured from the x axis to the terminal side of the angle.

Answer 4

Or you could measure it the other way, going clockwise instead of counterclockwise. That would look like this, in that case: