All the pairs ( x ,   y ) , that satisfy the inequality 2 s i n 2 x - 2 s i n x + 5 · 1 4 s i n 2…

All the pairs (x, y), that satisfy the inequality 2sin2x-2sinx+5·14sin2y1 also satisfy the equation:
  1. 2sinx=siny
  2. sinx=2siny
  3. sinx=siny
  4. 2sinx=3siny

Solution

Given inequality is
2sin2x-2sinx+5 4sin2y
sin2x-2sinx+1+42sin2y
sinx-12+42sin2y
2sin2y0, 2  &  sinx-12+42, 22
  Only equality holds
sinx-12+4=2sin2y=2
sinx-12+4=4sin4y=4 
sin2y=1     siny=1   &  sinx-12=0 sinx=1
siny=sinx

Asked in: JEE Main 2019 (10 Apr Shift 1)

Practice more Trigonometric Equations questions on Aicharya