Trig Function Help: Get Answers Now

[Eric Manuel]

thanks

 

[Jimmy Johnson]

Can you give the entire problem?

 

[Eric Manuel]

Can you give the entire problem?

all that's given is that

 

[MostlyHarmless]

What is the question? What are you asked to find?

 

[Eric Manuel]

What is the question? What are you asked to find?

what is =cos2x

 

[MostlyHarmless]

What is x supposed to be? Is the given problem in terms of t? Are you trying to solve for t and then plug that value in for x?

 

[Eric Manuel]

oh my bad its cos2t

its basically asking you to use the double angle formula
but I am not sure how to find those values

 

[Jimmy Johnson]

If you're simply trying to find t, then use cot = 1/tan... If you have a value for t why do you need to use the double angle identities?

 

[Eric Manuel]

to find what cos2t is ...

you can find what tan is from cot
then i drew a triangle and got the hypot to be sqrt(41)

but how do i do that math

formula for cos2t = cos^2(t) - sin^2(t)

 

[Jimmy Johnson]

Are you forbidden from using a calculator?

 

[Eric Manuel]

Are you forbidden from using a calculator?

teacher said u can use it
but need to know how to do it without one for test

 

[Jimmy Johnson]

Well that may have been useful information at the start...

you have cot = -5/4, find what tan is then recall tan = sin/cos ... or recall cot = cos/sin...

 

[Eric Manuel]

well i worked it out and i believe i got the answer to be 9/41

 

[Jimmy Johnson]

That's what I'm getting

 

[Jimmy Johnson]

You had the method right. Find the reference triangle then using toa soh cah find the sine, cosine or tan values to be substituted into the given identity.

You might find this link useful: http://www.mhhe.com/math/precalc/ba...tt01paga_s/ch06/downloads/pc/ch06section3.pdf