$( ) = 0 .9 ( − 1)( − 2) = 0 .10 00 .11 0 =0 ; −1=0 ; −2=0 =;= ;= .$( ) = 0 . 21 /∙ ( + 5) +5= 21 = ( + 5) /: 21 = + 5 /− 20 = 5 /: 20 5 = 20 = 120° 30°60°90° 2 =1 B 3 =3 .12 .2 : 360° 3