Answer:
4) BC=30.14
11)XZY≈47.5°
Explanation:
4) we use cosine law because we have two length known and one angle known
BC²=AB²+AC²-2ABcos55°
BC²=23²+20²-2*23*20cos55°=908.6
BC=√908.6= 30.14 cm
11) we use cosinee law because three length known
cosXZY=(22²+20²-17²)/(2×22×20)
cosXZY=0.676
XZY^= cos^-1 0.676
XZY^=47.5°