The derivative is . Thus a stationary point occurs either at or where . Since on the specified open interval, the only allowed cosine zeros are and . The five stationary abscissae are
Their ordinates are , , and , respectively. For completeness, shows that the inner pair are local minima and the outer pair are local maxima; is also a local maximum because .
Expanding the cross product gives . Comparing its three components in order from the last to the first gives , , and . Therefore
The nonzero value of permits division to find , and the resulting nonzero determines .
For a nonzero solution, the separable differential equation gives . Integrating yields , hence . The initial condition fixes , so
The zero solution omitted by division by cannot satisfy the given initial condition. Differentiating the displayed solution verifies .
A repeated linear factor requires both reciprocal powers. Write the partial fraction decomposition as
Multiplication by the common denominator gives . Setting gives , and setting gives . Comparing the coefficients of then gives . Thus
Use integration by parts twice. First,
The bracket containing vanishes, while the last definite integral is . Therefore
By the polynomial remainder theorem, the first polynomial remainder is . Equating it to gives .
For the separate polynomial long division, successively cancel the leading powers of the dividend. Subtracting leaves ; subtracting leaves ; subtracting leaves . Thus
The polynomial remainder also equals the dividend evaluated at .
The derivative of the parabola is , giving tangent line slope at . A normal line to a plane curve has the negative reciprocal slope, since its direction is orthogonal to a tangent vector. Hence
The point satisfies the equation, and the product of the two slopes is .

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