Chapter 7 - Section 7.3 - Double-Angle, Half-Angle, and Product-Sum Formulas - 7.3 Exercises - Page 561: 3

$\sin(2x)=120/169$ $\cos(2x)=119/160$ $\tan(2x)=120/119$

We know that by the trigonometric identity $\sin^2(x)+\cos^2(x)=1$ that $\cos(x) = \sqrt {1-(5/13)^2}=12/13$. Thus we use the identity $\sin(2x)=2\sin(x)\cos(x)$ and get $\sin(2x)=2\times12\times5/13^2= 120/169$. $\cos(2x)=\sqrt{1-(120/169)^2}=119/169$ $\tan(2x)=\frac{120/169}{118/169}=120/119$