Tolong bantuin ya.. no.1 dan no.2 Soal fisika kelas 10 sma

1). F = √(8)² +(4)² + 2.8.4 cos60
F= √64+16+2.32.1/2
F=√64+16+32
F= √112 N

2). a= 5,1i -2,3j
b= 1,0i
c= -3,1i +6,3j
--------------------------+
R= 3i +4j
Arahnya tan × = j/i = 4/3
X= 53°