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Unformatted text preview: come, we will have need to approximate the values of the inverse circular functions.
On most calculators, only the arcsine, arccosine and arctangent functions are available and they
are usually labeled as sin−1 , cos−1 and tan−1 , respectively. If we are asked to approximate these
values, it is a simple matter to punch up the appropriate decimal on the calculator. If we are asked
for an arccotangent, arcsecant or arccosecant, however, we often need to employ some ingenuity, as
the next example illustrates.
Example 10.6.5. Use a calculator to approximate the following values to four decimal places.
1. arccot(2) 2. arcsec(5) 3. arccot(−2) 4. arccsc(−5) Solution. 1. Since 2 > 0, we can use a property listed in Theorem 10.27 to write arccot(2) = arctan
In ‘radian’ mode, we ﬁnd arccot(2) = arctan 1 ≈ 0.4636.
2 . 2. Since 5 ≥ 1, we can invoke either Theorem 10.28 or Theorem 10.29 to write arcsec(5) =
arccos 1 ≈ 1.3694.
5 3. Since the argument, −2, is negative we cannot direc...
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