Question

Sina=3/5 find cos2a​

Answer 1

`\huge \purple{\therefore \cos2a} \orange{= }\red{(7)/(25) }`

Explanation:

`\because \cos2a =1 - 2 { \sin}^(2) a \\ \\ \therefore \cos2a =1 - 2 \bigg( { (3)/(5) }\bigg) ^(2) \\ \\\therefore \cos2a =1 - 2 * (9)/(25) \\ \\\therefore \cos2a =1 - (18)/(25) \\ \\\therefore \cos2a = (25 - 18)/(25) \\ \\ \huge \purple{\therefore \cos2a} \orange{= }\red{(7)/(25) } \\ \\`