# Weird assumption requirement in definite_integral

```
definite_integral(cos(y), y, 0, 3-x)
```

Instead of sin(3-x) it gives "ValueError: Computation failed since Maxima requested additional constraints; using the 'assume' command before evaluation *may* help (example of legal syntax is 'assume(x-3>0)', see `assume?`

for more details) Is x-3 positive, negative or zero?"

When the lower bound is not 0 (1 or something else), everything works correctly.

What is the reason for this and how to fix it?

This is reproducible in Maxima :

You may try to find iftis hasn't yet been reported in the (long) list of (Maxima) bugs for definite integrals and, if so, open yt another tickt.

You may also pragmatically work around :