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sicp-all-tasks/sicp/1_002e45

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Exercise 1.45: We saw in 1.3.3
that attempting to compute square roots by naively finding a fixed point of
y
x
/
y
does not converge, and that this can be fixed by average
damping. The same method works for finding cube roots as fixed points of the
average-damped
y
x
/
y
2
. Unfortunately, the process does not
work for fourth roots—a single average damp is not enough to make a
fixed-point search for
y
x
/
y
3
converge. On the other hand, if
we average damp twice (i.e., use the average damp of the average damp of
y
x
/
y
3
) the fixed-point search does converge. Do some experiments
to determine how many average damps are required to compute
n
th
roots as a
fixed-point search based upon repeated average damping of
y
x
/
y
n
1
.
Use this to implement a simple procedure for computing
n
th
roots using fixed-point, average-damp, and the
repeated procedure of Exercise 1.43. Assume that any arithmetic
operations you need are available as primitives.