lsgators028
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i'm trying to find the arcsecant of -.9, so i enter cos^-1 (1/-.9) into my calculator, but it comes up with an error in the domain. is there no solution or am i doing it wrong?
quick help
- Thread starter lsgators028
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Check your calculator's manual: what is the domain for the inverse cosine?
Also, note that the secant is the reciprocal of the cosine; the functions are inverses of each other, not the arguments. You need to invert the secants and cosines, not the -0.9s.
Eliz.
Also, note that the secant is the reciprocal of the cosine; the functions are inverses of each other, not the arguments. You need to invert the secants and cosines, not the -0.9s.
Eliz.
I entered in arccos(1/-.9) and got the same as if I entered in arcsec(-.9).
Make sure your calculator is set to radians and not degrees. The answer should be: pi-.467145308103i.
If it is set on degrees it will give you undef or maybe a domain error.
Make sure your calculator is set to radians and not degrees. The answer should be: pi-.467145308103i.
If it is set on degrees it will give you undef or maybe a domain error.
Daniel_Feldman
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Think of it this way:
It's asking for "arcsecant of -.9" Thus, you need to find the angle whose secant is -.9 Let's call that angle x.
Sec(x)=-0.9
1/cos(x)=-0.9
cos(x)=1/-0.9=-1.11
That's why stapel asked you to find the domain for the inverse cosine function: it's the same as the range for the cosine function (properties of inverse functions). Can the cosine of an angle ever be -1.11?
It's asking for "arcsecant of -.9" Thus, you need to find the angle whose secant is -.9 Let's call that angle x.
Sec(x)=-0.9
1/cos(x)=-0.9
cos(x)=1/-0.9=-1.11
That's why stapel asked you to find the domain for the inverse cosine function: it's the same as the range for the cosine function (properties of inverse functions). Can the cosine of an angle ever be -1.11?