"""
Exer 7.1 from A Primer on ...
"""
from math import *

class F:
    def __init__(self,a,w):
        self.a = a
        self.w = w

    def value(self,x):
        return exp(-self.a*x)*sin(self.w*x)

f = F(1.0,0.1)
print(f.value(x=pi))
f.a = 2
print(f.value(pi))


"""
Terminal> python F.py
0.01335383513703555
0.0005770715401197441
"""