Pi/2 radians different from 90 deg?

[Joe Horn]

In Home "pi/2" is not really pi/2, but only the first 12 significant digits of it, rounded off. The tangent of THAT number is what older firmware versions of Prime return in Home view.

If you want to find the tangent of EXACTLY pi/2, then use CAS view, in which "tan(pi/2)" returns +/- infinity. In general, use Home for 12-digit floating-point number crunching (like most other non-ancient HP models use) and use CAS for exact math and/or symbolic math.

Note that some recent firmware versions for the Prime return +/- infinity for tan(pi/2) even in Home view, even when "Intelligent Math" mode is turned off.