Thursday

March 5, 2015

March 5, 2015

Posted by **Pre Calc** on Friday, November 13, 2009 at 2:40pm.

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 -
**bobpursley**, Friday, November 13, 2009 at 2:55pmsec(-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 -
**Pre Calc**, Friday, November 13, 2009 at 3:02pmhow 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 -
**bobpursley**, Friday, November 13, 2009 at 4:22pmany trig function is periodic by 2PI.

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

**Answer this Question**

**Related Questions**

TRIG/ALGEBRA - 1) Find the exact value. Use a sum or difference identity. tan (-...

Algebra - Use properties of logarithms to find the exact value of each ...

Math - Use properties of logarithms to find the exact value of this expression. ...

pre-calculus - use a sum or difference formula to find the exact of the ...

Math - Use the sum or difference identities to find the exact value of each ...

trigonometry - Use fundamental Identities to find the exact value of the ...

Pre Calculus - ok I appologize for my stupidity... I'll answer your question... ...

Math(Correction) - Use the given function values and trigonometric identities (...

Math(Correction) - Use the given function values and trigonometric identities (...

trigonometry - 1.use a calculator to evaluate the expression cos31deg*cos149-...