Prove \(\displaystyle{\left({1}+{\sec{{x}}}\right)}{\left({1}+{\csc{{x}}}\right)}{>}{5}\) if \(\displaystyle{x}\in{\left[{0},{\frac{{\pi}}{{{2}}}}\right]}\).

Pizzadililehz

Pizzadililehz

Answered question

2022-03-31

Prove (1+secx)(1+cscx)>5 if x[0,π2].

Answer & Explanation

pautmndu

pautmndu

Beginner2022-04-01Added 10 answers

Let
y=(1+1+t21t2)(1+1+t22t)=2(1+t)22t(1t2)
as t+10
yt2t(y1)+1=0
As t is real the, discriminant
(y1)24y0
As the roots of y26y+1=0 are y=6±322=3±22
y26y+10 either y3+22 or y322
As 0<x<π2,cscxsecx1y>3y≠≤322

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