1∙1 = 22 1: 2 .19 .20 30°, 60°, 90° √3 √3 2 .√3R (√3R)2√3 √ 4= =4 √2 /∙ 3 4=3 12A = √2 /: √2 12A √2 = 144A2 2 2 2= 72 =