Descriptive geometry . Fig. 143. Construction (Fig. 143). Let it be required to pass the planethrough the line A. Assume any point con J; through c drawthe line D parallel to B. Pass the required plane Q throughthe lines A and D (Prob. 6, § 106).. Fig. 144. X, § 107] PARALLEL LINES AND PLANES 85 Special Case I. Suppose the second line is parallel to IIor V; then no auxiliary line is needed. Thus, in Fig. 144, letus find the plane which contains the line A and is parallel toB. The .ff-trace of any plane which is parallel to B must beparallel to Bh (§ 104). Hence, find the traces of A. DrawHQ th
Descriptive geometry . Fig. 143. Construction (Fig. 143). Let it be required to pass the planethrough the line A. Assume any point con J; through c drawthe line D parallel to B. Pass the required plane Q throughthe lines A and D (Prob. 6, § 106).. Fig. 144. X, § 107] PARALLEL LINES AND PLANES 85 Special Case I. Suppose the second line is parallel to IIor V; then no auxiliary line is needed. Thus, in Fig. 144, letus find the plane which contains the line A and is parallel toB. The .ff-trace of any plane which is parallel to B must beparallel to Bh (§ 104). Hence, find the traces of A. DrawHQ through sx parallel to Bh; draw VQ through tx and thepoint in which HQ intersects GL. Special Case II. Suppose that either the first or the secondgiven line is a profile line. The general solution will apply tothis case ; but if the problem be solved in this manner, a profileprojection will be necessary. A simple construction, by whichthe use of a profile projection may be avoided, is as follows : Let ab and C, Fig. 145, be the given lines. Through onepoint of the profile line, as a, draw an auxiliary line D parallelto the line C; through the other point, b, of ab, draw a second
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