Can we not just use the fact that ?
Does the question ask for the arc-length from to in the first quadrant.
If so the answer is .
That is the measure of the central angle times the radius which in this case is .
If it could be that the same formula works.
Now if then we need to know if we are still measuring in a counter-clockwise direction or not.
This directive the use of calculators and trigonometric tables is not allowed is impossible to follow except for a very, very few values of .