# Math Help - How do you find theta when given secant?

1. ## How do you find theta when given secant?

we reviewed this in class but i really didnt understand it very well. :[ and now we were given a take home test on it...
the problem is:
If sec theta =5/2, and theta is in quadrant one, find he value of theta to the nearest minute.
smeone please help!!

2. Originally Posted by DarkAngelxXxXx
we reviewed this in class but i really didnt understand it very well. :[ and now we were given a take home test on it...
the problem is:
If sec theta =5/2, and theta is in quadrant one, find he value of theta to the nearest minute.
smeone please help!!
secant is 1/cos

So $\frac{1}{\cos \theta} = \frac{5}{2}$

Can you do it now?

3. so do yu just do
cos theta = 2/5
theta= (cos^-1)(2/5)
theta= 1.159279....
then theta =1 degree 9 minutes 33.406 seconds
so the answer is 1 degree 9 minutes?

4. Exactly, because that is already in quadrant one.

EDIT: Thanks, HoI, of course your answer of 1.159... is in radians (which is in the first quadrant), sorry I automatically read your final answer in radians, too.

5. Originally Posted by DarkAngelxXxXx
so do yu just do
cos theta = 2/5
theta= (cos^-1)(2/5)
theta= 1.159279....
then theta =1 degree 9 minutes 33.406 seconds
so the answer is 1 degree 9 minutes?
Method is good, result is wrong! Your calculator is in radian mode. That is, arccos(2/5)= 1.159279... radians, not degrees.

Either put your calculator in degree mode or change that answer to degrees by multiplying by $\frac{180}{\pi}= \frac{180}{3.1415926}$