es a largeerror will often pass unnoticed. Great care should therefore be taken with per-pendiculars and parallels. 182. For estimating angles intermediate between 0° and 90°, we naturallyhalve the quadrant getting 45°. This is always readily tested, because it is a riseof one on a base of one as… … 70 hypothenuse B-30. By halving the 30° angle we get the 15°. Another familiar angle is the 60°. Here, thebase BD is half the hypothenuse B-60. By halving the angle between 60° and 90° we get the 75° angle. Allthese angles are in frequent use in engineering work and the student should become…
Mechanical drawing · Lettering
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