Evaluate that (sin^8A-cos^8A) + (4cos^2A-6cos^4A+4cos^6A)
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Step-by-step explanation:
Solution
verified
2.sinA
2.sinAcosA.cos2A.cos4A.cos8A
=
2
2
sinA
2sin2A.cos2A.cos4A.cos8A
=
2
3
sinA
2sin4A.cos4A.cos8A
=
2
4
sinA
2sin8A.cos8A
=
2
4
sinA
sin16A
=
2
4
sinA
sin2
4
A
∴cos57
∘
.cos14
∘
.cos28
∘
.cos56
∘
=
16cos83
∘
sin16×7
=
16cos83
sin112
∘
=
16cos83
∘
sin68
∘
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