Answer:
m∠B = [tex]97^{o}[/tex].
Step-by-step explanation:
Since the three sides of the triangle are given, then we apply cosine rule.
[tex]b^{2}[/tex] = [tex]a^{2}[/tex] + [tex]c^{2}[/tex] - 2ac Cos B
But, a = 660 cm, b = 680 cm, and c = 100 cm.
So that;
[tex]680^{2}[/tex] = [tex]660^{2}[/tex] + [tex]100^{2}[/tex] -2(660 x 100) Cos B
462400 = 435600 + 10000 - 132000 Cos B
462400 = 445600 - 132000 Cos B
132000 Cos B = 445600 - 462400
= -16800
Cos B = [tex]\frac{-16800}{132000}[/tex]
= -0.1273
B = [tex]Cos^{-1}[/tex] -0.1273
= [tex]97^{o}[/tex]
Thus, measure of ∠B is [tex]97^{o}[/tex].
