How can one argue that a, say, 30-degree angle is not a 30-degree angle just because he measures it enlarged, is beyond me. You really do not need to measure it, it is based on the principles of geometry from several thousand years ago. A 30-degree angle is a 30-degree angle is a 30-degree angle.
However, if one insists on measuring it, then he should be aware that any difference in the measured result can only be possible due to the precision of the measuring device and/or the operator.