Jawabanmu

2014-09-03T18:04:32+07:00
 R^{2} =  A^{2} +  B^{2} + 2.A.B.cos. \alpha 

 14^{2} = 8^{2} + 10^{2} +2.8.10.cos  \alpha
196 = 64+100+ (160.Cos α)
196= 164 +(160.Cos α)
Cos α =  \frac{196 - 164}{160} 

Cos α = 0,2
α = 78,46 (kalkulator)

semoga Membantu ^_^
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