He could have measured the angle of the desk&#x27;s diagonal makes with the longer side, that would give him tan(w&#x2F;l), no inches or centimetres required.<p>You do need radians, but that&#x27;s not a unit in the same way a &#x27;meter&#x27; is, you don&#x27;t need any kind of reference to know how much, say, 1 pi radians is. For most intents and purposes angles are unitless.