Reference: setApproxMode

setApproxMode(b) sets the approximation mode to b, true or false.

In approximation mode, very small numbers (such as 10^-30) are approximated to zero. In most computations this is desired, for in approximation mode sin(π) = 0, not -5.42101086243⋅10^-20.

However, when actually working with very small numbers, such as Planck's constant, approximation mode cannot, of course, be used.