.11 . ABC AD = BD ABC .180 . .12 C= .180° CFOE + 180 = 180 / 180 = 0 /+ = =1 –1 9| | 6 ∙ ( 1) = 24 / 6 3| | 2 ∙ | 1| = 4 /+2 (| | = 2) 9| | = 18 3| | = 6 3 .13 18 18 66 18 + 0 + 6 12 3 =3= .4 4