f(x) = 6·sin(8(x -π/2))
Step-by-step explanation:
A transformed sine function with amplitude A, period P, and horizontal shift S can be written as ...
f(x) = A·sin(2π/P(x -S))
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The equation for A=6, P=π/4, and S=π/2 is then ...
f(x) = 6·sin(8(x -π/2))
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Additional comment
The horizontal shift is equal to two full periods, so the shifted function is indistinguishable from the unshifted function.