If I have my calculator set to radians,how do I find the value of secant (- pi/3) on my calculuator TI-85?

Question

The trigonometric values that I am able to calculate are
sin, cos, and tan.
Secant, cosecant, and cotangent can also be calculated
using the calculator?
I am assuming that sin raised to the negative (-1)
is the inverse sine function?

Answer 1

Secant is the recipricol of the cosine, so enter pi / 3 = then press the change sign button (+/-). Then press the COS button, then the recipricol button (1/x).

Depending on the teacher, you might have to memorize this answer. The cosine of pi/3 is a special case. The answer is 1/2. The cosine of -x is the same as the cosine of x, the 1/2 is also the cosine of -pi/3. The secant is therefore 2.

Answer 2

sec(x) = 1 / cos(x)

cos(- x) = cos(x)

So sec(- pi / 3) = 1 / cos(- pi/3) = 1 / cos(pi/3) = 1 / (1/2) = 2

So switch the calculator into radians, then hit the "2" key.


Often the inverse of a function f(x) is written as f superscript -1, which looks a lot like raising to the -1 power, but they are two different concepts. A calculator will often have a key labelled "INV" for inverse of a function, and/or a key labelled "1/x" for reciprocal. (So for example, you might press "9" "INV" "x^2" in that order to calculate sqrt(9).)

Answer 3

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