Such large blocks of stone as were used in the casing of these pyramids could not have been completely dressed before setting; the back and ends, and the top and bottom beds were probably dressed off truly, and the face roughly scabbled off; but the true slope angle could not have been dressed off until the stone had been truly set and bedded, otherwise there would have been great danger to the sharp arises. * * * * * I shall now record the peculiarities of the 3, 4, 5 or Pythagorean triangle, and the right-angled triangle 20, 21, 29. § 7. PECULIARITIES OF THE TRIANGLES 3, 4, 5, AND 20, 21, 29. Fig. 30 to 35. PECULIARITIES OF THE TRIANGLES The 3, 4, 5 triangle contains 36° 52′ 11·65″ and the complement or greater angle 53° 7′ 48·35″ Radius 5 = 60 whole numbers.[6] Co-sine 4 = 48" Sine 3 = 36" Versed sine 1 = 12" Co-versed sine 2 = 24" Tangent 3¾ = 45" Secant 6¼ = 75" Co-tangent 6⅔ = 80" Co-secant 8⅓ = 100" Tangent + Secant = Diameter or 2 Radius Co-tan + Co-sec = 3 Radius Sine : Versed-sine :: 3 : 1 Co-sine : Co-versed sine :: 2 : 1 Figure 30 illustrates the preceding description. Figure 31 shows the 3·1 triangle, and the 2·1 triangle built up on the sine and co-sine of the 3, 4, 5 triangle. The 3·1 triangle contains 18° 26′ 5·82″ and the 2·1 triangle 26° 33′ 54·19″; the latter has been frequently noticed as a pyramid angle in the gallery inclinations. Figure 32 shows these two triangles combined with the 3, 4, 5 triangle, on the circumference of a circle. Footnote 6: 60 = 3 × 4 × 5 The 20, 21, 29 triangle contains 43° 36′ 10·15″ and the complement, 46° 23′ 49·85″. Expressed in whole numbers-- Radius 29 = 12180[7] Sine 20 = 8400 Co-sine 21 = 8820 Versed sine 8 = 3360 Co-versed sine 9 = 3780 Tangent = 11600 Co-tangent = 12789 Secant = 16820 Co-sec = 17661 Tangent + Secant = 2⅓ radius Co-tan + Co-sec = 2½ radius Sine : Versed sine :: 5 : 2 Co-sine : Co-versed sine :: 7 : 3 Footnote 7: 12180 = 20 × 21 × 29 It is noticeable that while the multiplier required to bring radius 5 and the rest into whole numbers, for the 3, 4, 5 triangle is twelve, in the 20, 21, 29 triangle it is 420, the key measure for the bases of the two main pyramids in R.B. cubits.[8] Footnote 8: 12 = 3 × 4, and 420 = 20 × 21 I am led to believe from study of the plan, and consideration of the whole numbers in this 20, 21, 29 triangle, that the R.B. cubit, like the Memphis cubit, was divided into 280 parts.