Use HP-like variable change for integration

[c3d]

When integrating 'sin(x)/x' between 0 and some other value, the expression is evaluating at 0, which causes a Divide by zero error.

On HP calculators, the problem does not exist. According to the HP15 Advanced Functions Handbook, this is achieved by doing a clever change of variable that also benefits in the case of periodic functions like sin because it turns the simple Romberg subdivision into a non-uniform one that minimizes aliasing effects.

This improvement was described by Nigel in an HP Museum Forum thread.