ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: Andiio on September 04, 2010, 02:16:32 pm

Title: Circular functions help please? :)
Post by: Andiio on September 04, 2010, 02:16:32 pm

For this question;

1. Evaluate
a. cot 2.4

Would the working out just be as follows?

cot 2.4
= 1/tan 2.4
= 23.859

Title: Re: Circular functions help please? :)
Post by: wiseguy on September 04, 2010, 02:19:11 pm

umm yea.

Title: Re: Circular functions help please? :)
Post by: Andiio on September 04, 2010, 02:22:00 pm

Okay sweet. So you don't have to take into account any radians or anything?

How would you do this question?
2. If cos(theta) = 0.92, sin (theta) = 0.39 and tan(theta) = 0.42 find the value of:
a) cot (pi+theta)

Teacher has been away for ages sigh.

Title: Re: Circular functions help please? :)
Post by: wiseguy on September 04, 2010, 02:27:52 pm

pi + theta in 3rd quadrant so ur tan is positive. so cot(pi+theta) is equal to 1/(0.42)


edit: fixed, thanks for pointing it out :)

Title: Re: Circular functions help please? :)
Post by: jasoN- on September 04, 2010, 02:29:15 pm

^^^^ theta is not 0.42, tan(theta)=0.42

cot(pi+theta)=1/tan(pi+theta)

As tan(pi+theta)=tan(theta) (quadrants)

cot(pi+theta)=1/tan(theta)
                  =1/0.42
                  =___

Title: Re: Circular functions help please? :)
Post by: Andiio on September 04, 2010, 02:48:18 pm

Thanks!

What about something like:

Write down the exact value of each:
d) cot 240 degrees

Are you supposed to put 1/tan(180+60) or something? I'm not sure what angle youre supposed to put in :/

Title: Re: Circular functions help please? :)
Post by: wiseguy on September 04, 2010, 02:52:24 pm

yep.

tan(180+60) is equivalent to tan(60) as tan(180)=0.

cot(240)=1/tan(60)=

Title: Re: Circular functions help please? :)
Post by: Andiio on September 04, 2010, 02:54:03 pm

Oh, but I thought you had to relate the angles you take to the quadrants?
As in, 180 - theta = 2pi - theta, pi + theta etc?