Respuesta :

we have that

The double angles formula is equal to

[tex]\cos (2\theta)=\cos ^2(\theta)-\sin ^2(\theta)[/tex]

and remember that

[tex]\begin{gathered} \sin ^2(\theta)+\cos ^2(\theta)=1 \\ \cos ^2(\theta)=1-\sin ^2(\theta) \end{gathered}[/tex]

therefore

substitute in the original expression

[tex]\begin{gathered} \cos (2\theta)=1-\sin ^2(\theta)-\sin ^2(\theta) \\ \cos (2\theta)=1-2\sin ^2(\theta) \end{gathered}[/tex]

therefore

The third option is incorrect

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