细节
Illustrations of Descriptive Geometry,
a 'pop-up' demonstration apparatus, unsigned, arranged with two planes and folding cord to show the intersection of the two planes, true length and inclination to show dehedral angle, the folding mahogany frames with brass hinges, 22½in. (57.1cm.) wide
a 'pop-up' demonstration apparatus, unsigned, arranged with two planes and folding cord to show the intersection of the two planes, true length and inclination to show dehedral angle, the folding mahogany frames with brass hinges, 22½in. (57.1cm.) wide