Answer:

Explanation:
Find angles

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Transform the expression using the sum-to-product formula

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Combine like terms

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Divide both sides of the equation by the coefficient of variable

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Apply zero product property that at least one factor is zero

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Cos (8A/2) = 0:
Cross out the common factor

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Solve the trigonometric equation to find a particular solution

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Solve the trigonometric equation to find a general solution

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cos(-2A/2) = 0
Reduce the fraction

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Simplify the expression using the symmetry of trigonometric function

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Solve the trigonometric equation to find a particular solution

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Solve the trigonometric equation to find a general solution

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Find the union of solution sets

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A = π/8 + nπ/4 or A = π/2 + nπ, n ∈ Z
Find the union of solution sets

I hope this helps you
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