Question

Pada segitiga abc ac= 3 ab=2 bc= akar 7 nikai cos A adalah

Answer 1

BC² = AB² + AC² + 2.AB.AC cos A
√7² = 2² + 3² + 2.2.3 cos A
7 = 4 + 9 + 12 cos A
7 = 13 + 12 cos A
7 - 13 = 12 cos A
-6 = 12 cos A
cos A = -6 / 12
cos A = -1/2

A = 120°