Just an additional observation in addition to David's.
Here's a small section of the equation:

equ = 0.77^Sin[E^x1^Sin[Log[2.53]]];

This is highly oscillatory. Are you sure this is correct?

If you are wondering if the function does oscillate...
If we shift the output down a little, say by 1, the output crosses the
x-axis 21 times as X1 varies only between 0 and 6.

IntervalBisection[equ, x1, Interval[{0, 6.}],0.0001]//Length

21

And jumps to 176 as the variable x1 varies between 0 and 10.

--
Dana DeLouis

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