40. a) yes, pythagorus' equation says A^2 + B^2 =C^2, If A=3, and B=4, then C would be 5 (the square root of 25 as 9+16=25). 3,4, and 5 are integers/rational so the perimeter would also be rational.
b) yes, if A=3, B=pi, C would be a combination of an irrational number making it irrational as well.
41. This is a special triangle, the sides are 1,2, and sqrt(3) (2 is the hypotenuse). The sqrt(3) is 1.732050808...., it appears to start repeating which means it is rational. Therefore the perimeter would be rational. Use this argument for why it is not irrational.