Sunday

February 1, 2015

February 1, 2015

Posted by **Cici** on Monday, June 16, 2014 at 7:38pm.

- Math: Trig -
**Damon**, Monday, June 16, 2014 at 7:58pmsec = 1/cos

so what angle has cosine = -1/2

that angle is 180 + or - 60 degrees

- Math: Trig -
**Damon**, Monday, June 16, 2014 at 8:00pmwhich is pi +/- pi/3

2 pi/3 or 4 pi/3

- Math: Trig -
**MathMate**, Monday, June 16, 2014 at 8:00pmarcsec(-2) is the same angle as arccos(-1/2)

The angle 2pi/3 is correct, so is 4pi/3.

Depending on the domain required, you may have to put in both values (for 0-2pi).

If that is not the problem, then you have to read carefully the instructions how to answer the question, how to type in the %pi; symbol, or the number of significant figures, etc.

- Math: Trig -
**Steve**, Monday, June 16, 2014 at 8:00pmsince cos pi/3 = 1/2,

sec pi/3 = 2

But, arcsec has principal values from 0 to pi, so arcsec(-2) = pi - pi/3 = 2pi/3.

Note: Some authors define the range of arcsecant to be ( 0 ≤ x < π/2 or π ≤ x < 3π/2 ), because the tangent function is nonnegative on this domain. This makes some computations more consistent.

So, you'd better check to see how your course defines the principal values. Apparently you were expected to provide 4pi/3 as the arcsec(-2)

- Math: Trig -
**Damon**, Monday, June 16, 2014 at 8:01pmPerhaps you were supposed to give both the quadrant 2 and quadrant 2 answers

- Math: Trig -
**Cici**, Monday, June 16, 2014 at 9:03pmOh, thank you so much Steve. I just found a very old sheet from class with the restrictions and you are right-- my teacher gave the unconventional one. I studied from online sources, which all gave the other range, so that's why I got it wrong. Thanks!

**Answer this Question**

**Related Questions**

Math 30 Trig - For the equation 4 cos theta - sqrt12 =0, where 0< theta < ...

Chemistry - Consider the decomposition of a metal oxide to its elements, where M...

grade 12 trig - If cos A-1=0, where 0<or= A< 2pi, then A=? The answer I ...

Calculus Verification - I just want to make sure im right. Find the derivative ...

algebra - 20 - 4/5x greater than or equal to 16. I did this and got the answer x...

Honors Chemistry - I'm doing what's called "test repair" for my class where we ...

math - g(x)= 1-2x-3, x< or equal to 0. x-18, x>6 find g(6). so I used the ...

math - A test had 200 questions .Each correct answer carried 2 marks.Each wrong ...

Trig - What is the period of f(x)=sin4x. I got pi/2 but on my answer list, it is...

trig - I got the following question marked wrong and I was wondering if someone ...