Pre Calc

posted by .

use properties of the trigonometric function to find the exact value of each expression. Do no use a calculator.

sec ( - pi/18) * cos (37 pi)/18

I do not see how to do this problem. Every time I do it out I get a reference angle of twenty degrees which isn't on the unit circle. I do it on my calculator and get answer of one. If you could show me how to do this problem that would be great. I think the part I'm getting stuck on is the - pi/8 there must be some other rule that I do not know about when there are negetives

• Pre Calc -

sec(-pi/18)*cos(37PI/18)
Remember that cos(-theta)=cos(theta)
so sec(theta)=sec(-theta)
sec(pi/18)cos(37Pi/18)
sec(2PI +Pi/18)cos(37PI/18)
sec(37pi/18)cos(37PI/18)
1/cos * cos= 1

• Pre Calc -

how did you go from the first line to the next in these lines

sec(2PI +Pi/18)cos(37PI/18)
sec(37pi/18)cos(37PI/18)
1/cos * cos= 1

• Pre Calc -

any trig function is periodic by 2PI.

sin (theta)=sin(theta+2PI)

Similar Questions

1. Math

Use properties of logarithms to find the exact value of this expression. Do not use a calculator. 6log6 8 - log6 7
2. Pre Calculus

ok I appologize for my stupidity... I'll answer your question... ok instructions to this problem In problems 77-88, use properties of the trigonmetric functions to find the exact value of each expression. Do not use a calculator 85. …
3. Math

Use the sum or difference identities to find the exact value of each trigonometric function. sec pi/12 Thanks :)
4. TRIG/ALGEBRA

1) Find the exact value. Use a sum or difference identity. tan (-15 degrees) 2) Rewrite the following expression as a trigonometric function of a single angle measure. cos 3x cos 4x - sin 3x sine 4x
5. pre-calculus

use a sum or difference formula to find the exact of the trigonometric function cos(-13pi/12)
6. Algebra

Use properties of logarithms to find the exact value of each expression. Do not use a calculator. 8^log 8^5
7. Pre-Calc

1) Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number. cos 12° cos 18° − sin 12° sin 18° And Find its exact value. 2) Use an Addition or Subtraction Formula to write the …
8. Pre-Calc

I am really struggling with how to do these problems, I posted them a few minutes ago but the answers/work shown was incorrect. 1) a) Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one …
9. Pre-Calc

Use the value of this trigonometric function to evaluate the indicated function. 1. cos(t) = 3/4 cos(-t) = ?
10. Pre-Calc

Hi, can someone please teach me how to solve this?

More Similar Questions