Question: An unruly integral

As an exercise to further familiarize myself with Maple, I would like to calculate the definite integral specified in the attached file. The integrand has an antiderivative, and a source lists the value of the integral as approximately 0.57... Based on the plot, this value is plausible according to a simple estimate (Pi/2 * 0.8 / 2). Following standard practice taught in school, I therefore calculated the difference between the values ​​of the antiderivative at the limits of integration. Surprisingly, the result is a complex number. What am I doing wrong? Did the internal Maple calculation switch to complex principal values?

testint5.mw

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