Can you give the entire problem?
all thats given is that
What is the question? What are you asked to find?
what is =cos2x
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?
oh my bad its cos2t
its basically asking you to use the double angle formula
but im not sure how to find those values
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?
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)
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
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...
well i worked it out and i believe i got the answer to be 9/41
That's what I'm getting
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
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