Trigonometric EquationHard
Question
The number of values of in the interval [-π, π] satisfying the equation cos θ + sin 2θ = 0 is-
Options
A.1
B.2
C.3
D.4
Solution
cosθ + sin2θ = 0
cosθ + 2sinqcosθ = 0
cosθ (1 + 2sinθ) = 0
⇒ cosθ = 0 or sinθ = - 1/2
θ = -
cosθ = cos
[-π, π]
θ = 2nπ ±
, θ = - 
,
cosθ + 2sinqcosθ = 0
cosθ (1 + 2sinθ) = 0
⇒ cosθ = 0 or sinθ = - 1/2
θ = -
cosθ = cos
[-π, π]θ = 2nπ ±
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