If (cos $\theta$ + sec $\theta$) = $\frac{5}{2}$ then (cos2$\theta$ + sec2$\theta$) = ?

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KollegeApply · Accepted Answer

bb($\frac{17}{4}$) Explanation: (cos $\theta$ + sec $\theta$)^2 = ($\frac{5}{2}$)^2 $\Rightarrow$ `cos^2$\theta$ + sec^2$\theta$ + 2 cos $\theta$ sec $\theta$ = $\frac{25}{4}$ $\Rightarrow$ (cos^2$\theta$ + sec^2$\theta$) + 2 = $\frac{25}{4}$ $\Rightarrow$ (cos^2$\theta$ + sec^2$\theta$) = ($\frac{25}{4}$ - 2) = $\frac{17}{4}$`

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