Sin⁶ + cos⁶ is equal to?
(a) 1 – 3sin² cos² θ
(b) 1 – 3sin cos θ
(c) 1+3sin² cos² θ
(d) 1
Sol:
Let a = sin² θ
b = cos² θ.
a³ + b³ = (a + b)³ – 3ab(a + b)
sin6 θ+sin6 θ=1-3 sin2 θ cos 2 θ
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