JEE Main | 2014Trigonometric EquationHard
Question
Let fk(x) = 
(sink x + cosk x) where x ∈ R and k ≥ 1.
Then f4(x) - f6(x) equals
(sink x + cosk x) where x ∈ R and k ≥ 1. Then f4(x) - f6(x) equals
Options
A.
B.
C.
D.
Solution
fk(x) = 
(sink x + cosk x)
f4(x) - f6(x) =
(sin4x + cos4x) - 
(sin6x + cos6x)
=[1 - 2 sin2 x cos2 x] - [1 - 3 sin2 x cos2x]
(sink x + cosk x)f4(x) - f6(x) =
(sin4x + cos4x) - (sin6x + cos6x)=
[1 - 2 sin2 x cos2 x] - [1 - 3 sin2 x cos2x]Create a free account to view solution
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