Solve the differential equation y"+ky = 0 using power series method. Then evaluate the first four terms (up to 6th degree) of the solution with even powers (coefficient of ao) at x = 0.543 if k = 19.

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Extracted text: Solve the differential equation y"+ky = 0 using power series method. Then evaluate the first four terms (up to 6th degree) of the solution with even powers (coefficient of ao) at x = 0.543 if k = 19.