IABI/IBCI=2/3
3IABI=2IBCI /:3
IABI=2/3 IBCI
IABI/IBCI=ctgα=2/3
ctgα=cosα/sinα=2/3
3cosα=2sinα /:3
cosα=2/3 sinα
sin²α+cos²α=1
sin²α+(2/3 sinα)²=1
sin²α +4/9 sin²α=1
13/9 sin²α=1 /*9/13
sin²α=9/13
sinα=3/√13
cosα=2/3 sinα
cosα=2/3 * 3/√13=2/√13
ctgα=2/3
tgα=1/ctgα
tgα=1/(2/3)=3/2
ICDI/IDAI=2/3
3ICDI=2IDAI /:3
ICDI=2/3 IDAI
ICDI/IDAI=tgβ=2/3
tgβ=sinβ/cosβ=2/3
3sinβ=2cosβ /:3
sinβ=2/3 cosβ
sin²β+cos²β=1
(2/3 cosβ)²+ cos²β=1
cos²β +4/9 cos²β=1
13/9 cos²β=1 /*9/13
cos²β=9/13
cosβ=3/√13
sinβ=2/3 cosβ
sinβ=2/3 * 3/√13=2/√13
tgβ=2/3
ctgβ=1/tgβ
ctgβ=1/(2/3)=3/2
