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  1. The value of
    cos3θ + sin3θ
    -
    cos3θ - sin3θ
    is equal to
    cosθ + sinθcosθ - sinθ
    1. - 1
    2. 1
    3. 2
    4. 0
Correct Option: C

cos3θ + sin3θ
+
cos3θ - sin3θ
cos θ + sinθcos θ - sinθ

=
(cos θ + sin θ)(cos²θ + sin²θ - cos θ . sin θ)
cos θ + sin θ

=
(cos θ - sin θ)(cos²θ + sin²θ + cos θ . sin θ)
cos θ - sin θ

= cos²θ + sin²θ – cosθ . sinθ + cos²θ + sin²θ + cosθ . sinθ
= 1 + 1 = 2



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