Trigonometric EquationHard
Question
Let θ, φ, ∈ [0, 2π] be such that 2cos θ (1 - sinφ) = sin2 θ
cos φ - 1, tan(2 π - θ) > 0 and - 1 < sin θ < -
Then φ cannot satisfy
cos φ - 1, tan(2 π - θ) > 0 and - 1 < sin θ < -
Then φ cannot satisfyOptions
A.

B.0 < φ < 

C.

D.
< φ < 2π
< φ < 2π Solution
0 cos θ (1 - sin φ) =
cosφ- 1 = 2 sin θ cos φ - 1
2 cos θ - 2 cos θ sin φ = 2 sin θ cosφ - 1
2 cos θ + 1 = 2 sin (θ + φ)
tan(π - θ) > 0 ⇒ tan θ < 0 and - 1 < sin θ < -
⇒ θ ∈
< sin (θ + φ) < 1
⇒ 2π +
< θ + φ <
+ 2π
2π +
-θmax < φ < 2π +
-θmin

cosφ- 1 = 2 sin θ cos φ - 12 cos θ - 2 cos θ sin φ = 2 sin θ cosφ - 1
2 cos θ + 1 = 2 sin (θ + φ)
tan(π - θ) > 0 ⇒ tan θ < 0 and - 1 < sin θ < -
⇒ θ ∈

< sin (θ + φ) < 1 ⇒ 2π +
< θ + φ <
+ 2π 2π +
-θmax < φ < 2π +
-θmin
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