Posted by kyu on .
Suppose that X is an angle in standard position and that X' is it's reference angle. If cosX = 4/ squareroot of 17. find the exact value of cosX'
is it 4/square root of 17?

Math Trig 
Reiny,
yes, X' would be in quadrant I, so its cosine would be positive.
cos X' = 4/√17