| 摘要 |
PURPOSE:To facilitate and to reduce cost by combining a simple triangular prism as the 1st prism and another simple triangular prism as the 2nd prism in one body. CONSTITUTION:A pentagonal Dach-prism 4 is cut with a plane including vertexes 41, 45, 46, and 44 and separated into an upper and a lower part as the 1st prism and 2nd prism respectively. The vertexes 41', 44', 45', and 46' of the 1st prism 5 are the same as the vertexes 41, 44, 45, and 46 of the 2nd prism 6 before cutting. Here, the 1st prism 5 and 2nd prism 6 are manufactured separately and independently and those two prisms are combined to obtain one pentagonal Dach-prism. The 1st prism 5 and 2nd prism 6 are both manufactured easily by cutting a triangular prism properly. Thus, the manufacture is simplified and the cost is reduced. |
