You should know what complementary and supplementary angles are, at least! I'll forgive you for not knowing coterminal, if you're learning trig for the first time. I actually don't know what you mean by "principle angle" -- probably we call it differently in the US. I'm going to guess that "principle angle" meansreference angle.

Two angles area)complementaryif they add up to 90°. Two angles aresupplementaryif they add up to 180°. I'll let you do those. (Although, I've never had to find the complement of an obtuse angle before. I have seen in one book that it's possible if the other angle is negative.)

Two angles arecoterminalif their difference is a multiple of 360°. So take 92° and add and subtract 360° repeatedly until you find all angles in the range you want.

For any given angle in standard position, areference angleis the smallest angle between the terminal side and the x-axis. Knowing these is helpful because the values of trig functions of angle is the same as the trig values of the reference angle of , though many will have a minus sign.

To find the reference angle for depends on the quadrant. Obviously, there is no need to find the reference angle of an angle in Quadrant I -- it's just .

For an angle in Quadrant II, the reference angle is .

For an angle in Quadrant III, the reference angle is .

For an angle in Quadrant IV, the reference angle is .

Now find the reference angle for .

I'll let you try this yourself. Just remember that the numbers I used above need to be converted to radians.b)

01