Explanation :
Law of Cosines, which states that in any triangle has sides of a, b, and c.
a is 3
c is not given
Therefore Length b is 10
c² = 3²+10²-2(3)(10)cos 34°
c² = 9 + 100 - 60cos 34°
c² = 109 - 60cos 34°
Using a calculator:
c² ≈ 109 - (60)(0.829)
c² ≈ 109 - 49.74
c² ≈ 59.26
Taking the square root of both sides:
c ≈ √59.26
c ≈ 7.69
c ≈ 8