Half angle identities....need a little help

[c.lewis]

Hey everyone, so im in the last week of this class and these are one thing I struggle with. Need help figuring these out

 

[tkhunny]

How are cosine and secant related?

How is tangent related to both sine and cosine?

 

[Steven G]

Can you write cos($\displaystyle \theta$/2) and tan($\displaystyle \theta$/2) in terms of sines and cosines? It is just the definition of cos($\displaystyle \theta$/2) and tan($\displaystyle \theta$/2)

Now can you label the three sides of a right triangle such that sec($\displaystyle \theta$) = $\displaystyle \sqrt{5}$?

Now using this triangle and the half angle formulas can you now answer the questions?