Question

$Iff\left(x\right)=co{s}^{2}x+se{c}^{2}x,then$

• A. f(x) <1
• B. f(x) = 1
• C. 1 < f(x) < 2
• D. f(x) 2

Answer 1

The correct option is D

f(x) 2

$Since,{(x-\frac{1}{x})}^2\ge 0,\forall xϵR,wehave{x}^2+\frac{1}{x^2}\ge 2andHence,f\left(x\right)=co{s}^{2}x+\frac{1}{co{s}^{2}x}\ge 2$