Use trigonometric identities to solve each equation within the given domain. sec(x) cos(3x) = 0 from [– π/2 , π/2] PLEASE SHOW WORK

Recall the triple angle identity for cosine:

cos(3x) = cos³(x) - 3 sin²(x) cos(x)

… = cos³(x) - 3 (1 - cos²(x)) cos(x)

… = 4 cos³(x) - 3 cos(x)

and the definition of secant,

sec(x) = 1/cos(x)

So we have

sec(x) cos(3x) = 0

(4 cos³(x) - 3 cos(x))/cos(x) = 0

cos(x) (4 cos²(x) - 3)/cos(x) = 0

If cos(x) ≠ 0 (this happens at the endpoints of the interval [-π/2, π/2]), we can simplify this to

4 cos²(x) - 3 = 0

cos²(x) = 3/4

cos(x) = ±√3/2

But since -π/2 < x < π/2, we know cos(x) > 0, so we ignore the negative case:

cos(x) = √3/2

==>   x = π/6 and x = -π/6

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step-by-step explanation: