Posted by **John** on Sunday, January 17, 2010 at 12:52pm.

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**, Sunday, January 17, 2010 at 2:05pm
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(45-30) ... (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)

## Answer This Question

## Related Questions

- Trig - Find the exact circular function value for: sec(23pi/6) I know the answer...
- Pre Calc - use properties of the trigonometric function to find the exact value ...
- trig - Let be an angle in standard position and the point (a, b) be the point ...
- trig - Find the exact value of the trigonometric function. -cot(pi/4 + 16pi)
- trig - use the unit circle to find the exact value for all the trig functions of...
- Math - Use the sum or difference identities to find the exact value of each ...
- Alg2/Trig - Find the exact value of the trigonometric function given that sin u...
- trig - Let P be the point on the unit circle U that corresponds to t. Find the ...
- Pre Cal - Let P be the point on the unit circle U that corresponds to t. Find ...
- Trig - Give the exact value of the trigonometric function: arctan(√3)

More Related Questions