side_1 = float (input(‘enter first side :’))
side_2 = float (input(‘enter second side:’))
side_3 = float (input(‘enter third side:’))
s = (side_1 + side_2 + side_3) / 2
d = (s * (s-a) * (s-b) * (s-c)) ** 0.5
print (“area of triangle is:”, d )
it is showing me error on the line “d = (s * (s-a) * (s-b) * (s-c)) ** 0.5” saying ---------------------------------------------------------------------------
NameError Traceback (most recent call last)
in
4
5 s = (side_1 + side_2 + side_3) / 2
----> 6 d = (s * (s-a) * (s-b) * (s-c)) ** 0.5
7 print (“area of triangle is:”, d )
NameError: name ‘a’ is not defined