[tex]\text{Given that, }\\\\~~~~~~~~~\sin \theta = \dfrac 35\\\\\implies \sin^2 \theta = \dfrac 9{25}\\\\\implies 2\sin^2 \theta = 2 \times\dfrac{9}{25}\\\\\implies 1-\cos 2\theta = \dfrac{18}{25}\\\\\implies \cos 2\theta = 1-\dfrac{18}{25}\\\\\implies \cos 2 \theta = \dfrac 7{25}[/tex]
