SSC CGL 2024 PYQ — Question 55

SSC CGL - 10 Sep 2024 - Shift 3 • Quantitative Aptitude • Q55

If 7 cos2 θ + 5sin2 θ − 6 = 0, (0o < θ < 90o), then what is the value of 1 + sec θ + tan θsec θ − tan θ\sqrt{sec\ θ\ +\ tan\ θ \over{sec\ θ\ -\ tan\ θ}}?

Show answer & explanation

Correct answer: A

Explanation

The correct answer is Option 1 i.e. 2\sqrt{2} + 2.

Given that,

⇒ 7cos2 θ + 5sin2 θ − 6 = 0

⇒ 2cos2θ + 5 cos2θ + 5 sin2θ - 6 = 0  [sin2θ + cos2θ = 1]

⇒ 2cos2θ + 5 - 6 = 0

⇒ 2cos2θ - 1 = 0

⇒ cos2θ = 1/2

⇒ cosθ = 1/√2

⇒ cosθ = cos 45

⇒ θ = 45

Now,  

⇒ 1 + sec θ + tan θsec θ − tan θ\sqrt{sec\ θ\ +\ tan\ θ \over{sec\ θ\ -\ tan\ θ}}

⇒ 1 + sec 45 + tan 45sec 45 − tan 45\sqrt{sec\ 45\ +\ tan\ 45 \over{sec\ 45\ -\ tan\ 45}}

⇒ 1 + 2 +12 −1\sqrt{\sqrt2\ +1 \over{\sqrt2\ -1}}

⇒ 1 + 2 +12 −1×2+12+1\sqrt{{\sqrt2\ +1 \over{\sqrt2\ -1}} \times {{\sqrt2+1}\over{\sqrt2+1}}}

⇒ 1 + (2 +1)222 −12\sqrt{{(\sqrt2\ +1)^2 \over{\sqrt2^2\ -1^2}} }

⇒ 1 + (2 +1)(\sqrt2\ +1)

⇒ 2+2\sqrt2 + 2