Answer:
m∠B ≈ 70.8°
Step-by-step explanation:
The Law of Cosines relates three sides of a triangle and the angle opposite one of them.
Setup
The law of cosines tells you ...
b² = a² +c² -2ac·cos(B)
Solving for angle B, we get ...
B = arccos((a² +c² -b²)/(2ac))
where 'a' and 'c' are the sides adjacent to the angle of interest. We want angle B, so we can fill this formula as follows:
B = arccos((13² +11² -14²)/(2·13·11))
Solution
B = arccos(94/286)
B ≈ 70.812°
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Additional comment
Another angle can be found using the Law of Sines.
A = arcsin(sin(70.812°)×13/14) ≈ 61.281°
Then angle C is ...
C = 180° -70.812° -61.281° = 47.907°
