7 1/2 * 2 1/2 = 15/2 * 5/2 = 75/4 = 18 3/4
5 5/6 * 6 1/6 = 35/6 * 37/6 = 1295/36 = 35 35/36
4 1/5 * 2 3/7 = 21/5 * 17/7 = 357/35 = 10 7/35 = 10 1/5
3 1/8 * 5 3/16 = 25/8 * 83/16 = 2075/128 = 16 27/128
9 5/6 * 3 1/6 = 59/6 * 19/6 = 1121/36 = 31 5/36
Tg(x — п/4) — tg( x + п/4) =sin(2x)/(cos(x — п/4)*cos(x + п/4))=sin2x/(0.5(cos(-п/2)+cos2x))=2sin2x/cos2x=2tgx2x