tan(pi/2) is undefined, like 1/0. http://math.stackexchange.com/questions/189621/is-tan-pi-2-undefined-or-infinity http://math.stackexchange.com/questions/1896

tan(pi/2) is undefined, like 1/0. http://math.stackexchange.com/questions/189621/is-tan-pi-2-undefined-or-infinity http://math.stackexchange.com/questions/189621/is-tan-pi-2-u...