NTA Abhyas JEE Main2020MathematicsTrigonometric EquationsPractice
The solution of the equation tan 2 x - 1 - 1 = 1 + cos 2 x is
Options
- Ax = n π - π 2
- Bx = n π ± π 4
- Cx = n π ± π 3
- Dx = n π
Correct answer
C. x = n π ± π 3
Step-by-step solution
1 tan 2 x - 1 = 1 + cos 2 x ⇒ cos 2 x sin 2 x - cos 2 x = 1 + cos 2 x ⇒ 1 + cos 2 x 2 - cos 2 x - 1 + cos 2 x = 0 1 + cos 2 x - 1 2 cos 2 x - 1 = 0 ⇒ 1 + cos 2 x = 0 or 1 + 1 2 cos 2 x = 0 ⇒ cos 2 x = - 1 or - 1 2 ⇒ 2 x = 2 n π ± π or 2 n π ± 2 π 3 ⇒ x = n π ± π 2 or n π ± π 3 But for x = n π ± π 2 , cos x = 0 and hence tan x is not defined ⇒ x = n π ± π 3