| 摘要 |
PROBLEM TO BE SOLVED: To rapidly draw an accurate angle line without adding a mark. SOLUTION: An arbitrary length of a side of a square shaped object is selected, and a vertical line to divide the selected arbitrary length into two equal parts is drawn. When the arbitrary length side is recessed, two end portions are formed. When these ends are brought into contact with the circumference part of the edge of a protractor, a chord of a length equal to the recessed width is formed on the circumference part. The vertical bisector of the chord passes through the center of a circle, and the line extending the vertical bisector of the chord matches to the vertical line dividing the arbitrary length into two. An angle can be selected by matching the vertical line to an angle scale of the protractor and an accurate angle line can be drawn rapidly without putting a mark, by removing the protractor and matching a triangle to the vertical line. COPYRIGHT: (C)2009,JPO&INPIT
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