Answer:
38°
Step-by-step explanation:
The triangle solver app on your calculator, phone, or tablet can solve this for you readily. There are on-line triangle solvers, too.
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For solution "by hand", the Law of Cosines is useful. It tells you ...
a^2 = b^2 + c^2 -2ab·cos(A)
Then the angle A can be found as ...
cos(A) = (b^2 +c^2 -a^2)/(2ab) = (3^2 +7^2 -5^2)/(2·3·7) = 33/42 = 11/14
A = arccos(11/14) ≈ 38°
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In formulas like the Law of Cosines or the Law of Sines, the uppercase letters stand for the measures of angles, and the lowercase letters stand for their opposite side lengths.
