Mathematical questions with their solutions, from the "Educational times" Volume 35
W. J. C. Miller
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1872 Excerpt: ...all the parallels (modulus r) of curves traced on the ellipsoid (tubular surfaces). The singular solution represents the particular parallel (modulus r). But now impose the further condition that the ellipsoid and the surfaces have a common normal at corresponding points, so that and we have further the universal equality dz = pd.s + qdy (12). The elimination of p, q, r from (9), (10), (11), and (12) ought to give the previous result as the differential equation. To show this, we may compare (7) with (9). These equations become identical by the equalities z_ LP = iL, y-rJL _ JhL, Z+1=JL p e+a v e + b' v e+c But substituting the value of--, thence obtained in terms of 6, in (10) and (11), we get p--( + a), q _ =&±p/t K" b (» + »)' (9 + b) z' and by (12) regain the equation (8). II. Solution by Professor Twnsend. Since, from the equation of the ellipsoid, for any point (z, y, z) on the parallel, /rTA cos a'-/yF cos/92 /zTA cos-y.where ± k = the parameter of the parallel, and a, B, y the direction angles of its normal at x, y, z; therefore, substituting in this equation for cos a, cos 0, cos 7 their values--,,--, divided each by tho square root dx dy dz of the sum of their squares, and clearing the result of the radical invelved, we have at once the differential equation required; which, as the radical enters only as the divisor of k in the uncleared equation, is consequently the same for the two parallels equidistant in opposite directions by the intervals ±A from the original surface. By a similar process, substituting for x, y, z, in the equation of any surface, x±kcosa, y±k con $, z±£cos-y, changing cosa, &c., into the above values, and clearing the result of the radical invelved, we obtain the comm...