Engineering
Mathematics
Arithmetic Mean Geometric Mean and Harmonic Mean
Question

Let f(x)=secx+2cos2x+1,x∈(−π2,π2)  , the minimum value of f (x) is

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Solution

f (x) = sec x + 4cos2 x – 1

secx2,  secx2,4cos2x,A.M.≥G.M.

sec x +4 cos2 x ≥ 3

sec x + 4 cos2 x – 1 ≥ 3 – 1