Answer:
[tex] \huge \purple{\therefore \cos2a} \orange{= }\red{\frac{7}{25} } [/tex]
Step-by-step explanation:
[tex] \because \cos2a =1 - 2 { \sin}^{2} a \\ \\ \therefore \cos2a =1 - 2 \bigg( { \frac{3}{5} }\bigg) ^{2} \\ \\\therefore \cos2a =1 - 2 \times \frac{9}{25} \\ \\\therefore \cos2a =1 - \frac{18}{25} \\ \\\therefore \cos2a = \frac{25 - 18}{25} \\ \\ \huge \purple{\therefore \cos2a} \orange{= }\red{\frac{7}{25} } \\ \\[/tex]
