What are the 3 base units of measurement ?

In the SI (International, metric) system of measurement, they are the Kilogram of mass, the Meter of length, and the Second of time.  

With mass, length, and time, you can combine them in enough ways to measure ALMOST everything that can be measured in the physical world, like speed, velocity, acceleration, momentum, area, volume, force, energy, pressure, etc.

'Almost'. You still need a few more to wrap things up.  The other quantities (and their SI units) are:  Electric charge (the Coulomb), temperature (the Kelvin), amount of a substance (the Mol), and luminous intensity (the Candela).  You can't build these with only mass, length, and time.

pythagoras' theorem

square root (-5^2+9^2)

square root (25+81)

square root (106)

angle is tan^-1(9/5)

neg x, pos y