<h3>Answer: 22 degrees</h3>
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Explanation:
Use the law of cosines to isolate angle A
a^2 = b^2 + c^2 - 2*b*c*cos(A)
3^2 = 5^2 + 7^2 - 2*5*7*cos(A) ... plug in a=3, b=5, c=7
9 = 25 + 49 - 70*cos(A)
9 = 74 - 70*cos(A)
74 - 70*cos(A) = 9
-70*cos(A) = 9 - 74 .... subtract 74 from both sides
-70*cos(A) = -65
cos(A) = -65/(-70) ... divide both sides by 70
cos(A) = 13/14
A = arccos(13/14) .... apply the arcosine function to both sides
A = 21.7867892982619
This rounds to 22 degrees
