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JEE Advanced · Mathematics · 8. Trigonometric Equations

Let M denote the determinant of a square matrix M. Let g:0,π2 be the function defined by gθ=fθ-1+fπ2-θ-1 where fθ=121sinθ1-sinθ1sinθ-1-sinθ1+sinπcosθ+π4tanθ-π4sinθ-π4-cosπ2loge4πcotθ+π4logeπ4tanπ
Let px be a quadratic polynomial whose roots are the maximum and minimum values of the function gθ, and p2=2-2. Then, which of the following is/are TRUE ?

  1. A P3+24<0
  2. B P1+324>0
  3. C P52-14>0
  4. D P5-24<0
Verified Solution

Answer & Solution

Correct Answer

(C) P52-14>0

Step-by-step Solution

Detailed explanation

Given,
fθ=121sinθ1-sinθ1sinθ-1-sinθ1+sinπcosθ+π4tanθ-π4sinθ-π4-cosπ2loge4πcotθ+π4logeπ4tanπ
fθ=121sinθ1-sinθ1sinθ-1-sinθ1+0cosθ+π4tanθ-π4sinθ-π40loge4π-tanθ-π4-loge4π0
Here we used cosθ+π4=-sinθ-π4
And tanθ-π4=-cotθ+π4
And loge4π=-logeπ4
Also sinπ=-cosπ2=tanπ=0
So, fθ=121sinθ1-sinθ1sinθ-1-sinθ1+skew symmetric
fθ=1+sin2θ
So, gθ=sinθ+cosθ
Now maximum and minimum values are 2 and 1 respectively.
Now quadratic polynomial will be Px=ax-2x-1, where aR-0,
But given P2=2-2 , so a=1.
 Px=x-2x-1
Now solving all options we get,
P3+24=3-324·2-14<0
P1+324=1-24·32-34<0
P52-14=2-14·52-54>0
P5-24=5-5241-24>0
From JEE Advanced
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