------------------------------**Problem:**

Given a slider x-value find and plot the equation of the line tangent to a given curve f(x) together with the function f(x).

------------------------------

```
from visual import *
def function():
print "Type in your function."
return raw_input("Enter it again, %s." % (yn))
from visual.graph import * # import graphing features
funct1 = gcurve(color=color.cyan) # a connected curve object
for x in arange(0., 8.1, 0.1): # x goes from 0 to 8
funct1.plot(pos=(x,5.*cos(2.*x)*exp(-0.2*x))) # plot
from visual.controls import *
# Create "call-back" routines, routines that are called by the interact
# machinery when certain mouse events happen:
s1 = slider(pos=(-15,-40), width=7, length=70, axis=(1,0,0), action=lambda:100)
s1.value = 70 # update the slider
while True:
rate(10)
print str(s1.value)
```