Jawabanmu

2013-12-15T12:13:43+07:00
 \frac{selisih}{resultan} =   \sqrt{13} 
 
 selisih=  \sqrt{13} . resultan 

  R= \sqrt{ F1^{2}+ F2^{2}+2.F1.F2 cos \alpha } 

 selisih =  \sqrt{ F1^{2}+ F2^{2}-2.F1.F2 cos \alpha} 
 
 \sqrt{ F1^{2}+ F2^{2}-2.F1.F2 cos \alpha} =  \sqrt{13} . \sqrt{ F1^{2}+ F2^{2}+2.F1.F2 cos \alpha } 

  F1^{2}+ F2^{2}-2.F1.F2 cos \alpha = 13. (F1^{2}+ F2^{2}+2.F1.F2 cos \alpha) 

  2F^{2} - 2F^{2} cos  \alpha  = 13 (2F^{2} + 2F^{2} cos  \alpha) 

  2F^{2} - 2F^{2} cos  \alpha = 26F^{2} +26F^{2} cos  \alpha





-24F^{2} = 28F^{2} cos  \alpha 
 
\frac{-24}{28} = cos \alpha 

 -0,8 = cos  \alpha  



kalo gak salah segini. cek lagi ya :)