#
Lambert's formula
^{
}

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)
```