(3с + 5d)/5*7*cd + (c-3d)/3*7*cd = 3(3c-5d)/5*7*3*cd + 5(c-3d)/ 3*7*5*cd =
(9c - 15d +5c -15d)/ 3*5*7*cd = 14c/15*7*cd = 2c/15cd = 2/15d.
1- cos(B) + cos(2B)=cos^2(B)+sin^2(B)-cosB+cos^2(B)-sin^2(B)=
=2cos^2(B)-cosB =cos(B)*(2cos(B)-1)
0.65км=650м = 65000 см =650000 мм