A) cosinus = côté adjacent/hypoténuse
cos 40° = AB/7 => 0,766.. = AB/7 => AB = 7 x 0,766..= 5,36
b) sinus = côté opposé/hypoténuse
sin 55° = 8/AB => 0,819..= 8/AB => AB = 8/0,819 = 9,77
c) tangente = sinus/cosinus = côté opposé/côté adjacent
tan 70° = 3/AB => 2,747.. = 3/AB => AB = 3/2,747..= 1,09