Question 971852
After they had the Pythagorean theorem,
they knew that things like the 3-4-5 
right triangle existed, because
{{{ 5^2 = 3^2 + 4^2 }}}
That means they then knew all the 
trig functions of the angles, like
{{{ tan(theta) = 3/4 }}} for the angle 
opposite the side {{{ 3 }}} units long