Răspuns:
cos A=0.508 cos B=0.385 cos C =0.600
Explicație pas cu pas:
AB =13 BC=14 AC= 15
Per tr= 42 p=21
Aria tr =(21(21-13)(21-14)(21-15))^0.5=7056^0.5=84
Hb= 2*84/AC=2*84/15=11.2
Ha= 2*84/BC=2*84/14=12
Hc= 2*84/AB = 2*84/13= 12.92
sin A= Hb/AB = 11.2/13=0.86
sin B= Hc/BC = 12.92/14=0.923
sin C= Ha/AC= 12/15 = 0.8
cos A = (1-0.86^2)^0.5= 0.508
cos B = (1-0.923^2)^0.5= 0.385
cos C = (1-0.8^2)^0.5=0.6