1982 AHSME Problem 23

The lengths of the sides of a triangle are consecutive integers, and the largest angle is twice the smallest angle. The cosine of the smallest angle is

\text{(A)}\frac{3}{4}\qquad \text{(B)}\frac{7}{10}\qquad \text{(C)}\frac{2}{3}\qquad \text{(D)}\frac{9}{14}\qquad \text{(E)}\text{none of these}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.