A few months ago, I did a brief rant about a mechanic/fabrication test question that used angle in reference to a distance.

Diameters.

At issue was the size of an angle in reference and relation to a diameter — a diameter that would be on the order of a few fractions of an inch to a few inches. A bend radius of a wire or wire bundle.

It has now occurred to me that, yes, you most absolutely can use an angle to measure a radius.

We use the concept of angular diameter in calculating long-range distances of several hundred meters. Rather, in that regard, we use the (forced) perspective and a few simple trigonometric functions (sine, cosine, tangent) to measure a distance to a target.

We often use angular diameter in astronomy to determine the distance to a star or to a galaxy.

I will stand, therefore, partially corrected.

I still think it’s abnormal to refer to the angle of a radius.