Finding exact values

[kelleynicole30]

Find the exact values of sin(theta/2), cos(theta/2), and tan(theta/2) for the given conditions.

sec(theta)=-4; 180 deg < theta < 270 deg





I know this is in quadrant 3 and I know I am suppost to plug in the multiple angle formulas for the equation. I calculated that the triangle has a hyp of -4 and sides of 1. Whenever I try to plug them in I get lost in all the fractions. Help would be appreciated.
Thanks.

 

[Loren]

sec(theta)=-4; 180 deg < theta < 270 deg

Therefore cos(theta) = -1/4.
$\displaystyle \sin \frac{\theta}{2} = \pm \sqrt{\frac{1-\cos \theta}{2}}$
Now, plug the -1/4 into the equation in place of cos(theta) and simplify. Consider what quadrant sin(theta)/2 is in to determine its sign.

 

[kelleynicole30]

I got - square root(5)/2

 

[Deleted member 4993]

I got - square root(5)/2

<<< You have to find three values for three expresions -- which one did you find?

You have "-" in front of the number -- is that for hyphen, or, does it indicate negative value?