What is the midline equation of y = - 9cos(pi/2 * x - 6) + 8 ? ?

The power of the root of the power of a variable can be written as a rational power by creating a rational exponent that is the product of the powers divided by the root. The rational exponent should be reduced to lowest terms. For example, the seventh power of the sixth root of the fifth power of x will be x^(7*5/6) = x^(35/6).
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