verifying a trig identity

[denisecarrel]

I am having a hard time understanding how to verify : sec(alpha+theta)=sec alpha sec theta / 1-tan alpha tan theta. Thanks!

 

[Deleted member 4993]

I am having a hard time understanding how to verify : sec(alpha+theta)=sec alpha sec theta / 1-tan alpha tan theta. Thanks!

Start with the right-hand-side and convert everything to sines and cosines.

Now simplify through algebra...

Please share your work with us, indicating exactly where you are stuck - so that we may know where to begin to help you.