Posted by John on .
Find the exact value of the trigonometric function:
sec(pi/12)
I am not sure how to answer this off the unit circle.

trig 
Reiny,
You should know that
sec (pi/12)
= 1/cos(pi/12)
= 1/cos(pi/12)
You might find it "easier" to visualize degrees than radians, if so, the
pi/12 radians = 15º
so we need cos 15º
cos15 = cos(4530) ... (I am dropping the º symbol for easier typing)
= cos45cos30 + sin45sin30
= (√2/2)(√3/2) + (√2/2)(1/2)
= (√6 + √2)/4
and
cos(pi/12) = 4/(√6 + √2)