| 摘要 |
A protractor comprising a generally flat protractor disc having a straight edge portion and a semi-circular portion. An arm member is pivotally secured at one end to a central section of the straight edge portion and overlies the front surface of the semi-circular portion at the other end. The arm member has a straight drawing edge that aligns with angle indicia on the semi-circular portion. An arcuate member extends outwardly from the front surface of the semi-circular portion. The arm member has recess in a rear surface thereof that receives the arcuate member therein. The relationship between the depth of the recess and the distance that the arcuate member extends from the front surface of the semi-circular portion is such that the arm member is spaced from the indicia on the front surface.
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