I find a picture helps, here
Let BAC = 47°
Note that angles ABO and ACO each = 90°
So....the quadrilatral formed by ABOC has interior angles that will sum to 360°
And we know three of the angles and we are trying to find angle BOC
So
47 + 90 + 90 + BOC = 360 .......simplify
227 + BOC = 360 subtract 227 from both sides
BOC = 133
And since this is a central angle, it has the same measure as the arc we are interested in, namely, minor arc BC......so....the measure of the arc intercepted by the tangents = 133°