Perspective and geometrical drawing adapted to the use of candidates for second and third-class teachers' certificates . BOG Fig. 81. Let AD be the given altitude ; through A, draw EAF per- GEOMETRICAL DEAWING. 115 pendicular to AD; with centre A describe any semicircleEGHF, and with centre F and distance FA, describe arc tocut arc GH in H; also with centre E and same distance de-scribe arc to cut GH in G. Join AG and AH, and producethem to meet BC in B and C: then ABO will be the equi-lateral triangle required. (Fig. 81.) No. 1^.—{a) To draw, from a given point in a straight line,an angle equ
Perspective and geometrical drawing adapted to the use of candidates for second and third-class teachers' certificates . BOG Fig. 81. Let AD be the given altitude ; through A, draw EAF per- GEOMETRICAL DEAWING. 115 pendicular to AD; with centre A describe any semicircleEGHF, and with centre F and distance FA, describe arc tocut arc GH in H; also with centre E and same distance de-scribe arc to cut GH in G. Join AG and AH, and producethem to meet BC in B and C: then ABO will be the equi-lateral triangle required. (Fig. 81.) No. 1^.—{a) To draw, from a given point in a straight line,an angle equal to a given Let BAG be given angle and let the given point be at D;with centre A and any distance less than a side describe anarc CB ; with centre D and distance equal to AB describe arcEF; with centre E and distance equal to BC describe an arcto cut EF in F; join DF: then the angle EDF will be equalto the angle BAG. (Fig. 82.) (h) Within a given circle to construct a triangle similar toanother triangle. (Triangles are similar when the angles inone are equal to the angles in the other, each to each. Theyare similarly situated when the sides of one are parallel to thesides of the other, each to each. These are called homologoussides.) Let ABC be the given circle and LHK, the given any point C, draw a tangent DE, and describe a semicircleDE; with centre H, and any distance HM, describe an arc,and with centre K and same distance describe an arc. MakeEG = NO and DF = MO; join CF and CG, and produce tham 116 DRAWING. to the circumference in A and B; join AB, completing thetriangle required
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Keywords: ., bookcentury1800, booksubjectgeometricald, booksubjectperspective
