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Kelas 11 Matematika
Bab Trigonometri Lanjut

Cos a = (AB² + AC² - BC²)/(2 . AB . AC)
Cos a = (16² + 10² - 14²) / (2 . 16 . 10)
Cos a = (256 + 100 - 196)/320
Cos a = 160/320
Cos a = 1/2
a = 60°

BC^2=AC^2+AB^2-2AC.AB.COS A
14^2=10^2+16^2-2.10.16.COS A
14^2=10^2+16^2-320COS A
196=100+256-320COS A
COS A=160/320
COS A =1/2
A = 60