esli A=30 gradusov to C=1/2AC=6cm,AB=sqrt(108)
питагора---BD^{2}=(12-x) ^{2}+36 (BDC)
BD^{2}=x^{2}+108
(12-x) ^{2}+36 =x^{2}+108
144-24x+x^{2}+36-x^{2}-108=0
-24x=-72
x=3 (AD)
DC=12-AD=12-3=9
esli A=30 gradusov to C=1/2AC=6cm,AB=sqrt(108)
питагора---BD^{2}=(12-x) ^{2}+36 (BDC)
BD^{2}=x^{2}+108
(12-x) ^{2}+36 =x^{2}+108
144-24x+x^{2}+36-x^{2}-108=0
-24x=-72
x=3 (AD)
DC=12-AD=12-3=9