#
Lambert's formula
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}

A continued fraction representation of the tangent function was published in 1770 by the German mathematician J.H. Lambert:

```
tan x = x
---------------
1 - x²
-----------
3 - x²
-------
5 - ...
```

where x is in radians. Define a procedure (tan-cf x k) that computes an approximation to the tangent function based on Lambert's formula. K specifies the number of terms to compute, as in exercise 1.37 .

```
(check-equal? (tan-cf (/ pi 4) 100) 1.0)
(check-equal? (tan-cf 0 10) 0.0)
(check-equal? (round (* 100 (tan-cf (/ pi 3) 100))) 173.0)
```