SCalc 2.0

This program implements a number of specialized calculators for solving problems encounter frequently. They're the sorts of things that would normally be implemented on a programmable calculator.
It includes:
a/b = c/d (solve ratios)
1/Z = 1/x1 1/x2 ... (parallel resistors, series capacitors)
RSS = sqrt (x1*x1 x2*x2 ...) (root-sum-square)
RMS = sqrt [(x1*x1 x2*x2 ...)/n] (root-mean-square)
max, min, median, mean and standard deviation
conversions between fractional degrees and degree:minutes:seconds
I'll welcome any suitable additions to this tool.