Answer:
b = 38.22
Explanation:
In the given triangle ABC, a = 3, b = 5 and c = 7 is given.
We have to find the measure of angle b.
To get the measure of any angle we will apply cosine rule in the triangle.
b² = a² + c² - 2ac(cosb)
5² = 3² + 7² - 2×3×7×cosb
25 = 9 + 49 - 42×cosb
25 = 58 - 42cosb
-42cosb = 25 - 58 = -33
cosb =

cosb = 0.7856

b = 38.22
b = 38.22 is the correct answer.