Answer:
b = 11.0
Step-by-step explanation:
From the given properties of the triangle,
b = AC
Applying the cosine rule, we have;
[tex]b^{2}[/tex] = [tex]a^{2}[/tex] + [tex]c^{2}[/tex] - 2acCos B
= [tex]10^{2}[/tex] + [tex]7^{2}[/tex] - 2(10 x 7) Cos 80
= 100 + 49 - 140 x 0.17365
= 149 - 24.311
= 124.689
b = [tex]\sqrt{124.689}[/tex]
= 11.1664
b = 11.0
